iOS 15.4 - iMessage won't active. Error message - "An error occurred during activation."

My solution is the one that has worked and I haven’t had any issues since.

I removed the cellular plan from T-Mobile from the phone and I then contacted T-Mobile and had them reassign my Eid to my plan and that solved the problems. Restarted the phone waited for the I haven’t had any issues ever since.

here are the steps that I posted a few weeks ago.

I was trying to troubleshoot this issue (spend a night without cell phone service.)

But i was able to get it working again.

1. Have another phone handy cause you will need it to contact you provider (t-mobile in my case)
2. Make sure that you have access to wifi cause you will need it to gain service back.
3. I removed the cellular plan from my account. so that my phone lost service completely. and no service was associated to my phone.
4. Called tmobile from the other phone and asked them re input the EID in their system on their end.
5. waited a few moments and went to add the cellular plan back to my account and then everything starting filling back in.
6. went to reactivate imessage and facetime and it worked with no issue.

Seems like that fixed the problem.

I'm not sure if the people having this problem are using esim or not but this seems to have done the trick and i am able to get and receive imessage and facetime calls again.

I can now confirm that after 5 days the solution posted by JustJared works. For some it will be faster to get a hardware SIM at a local T-Mobile store, but I wanted to keep the slot open as I sometimes need to purchase a cheap Data only SIM while traveling internationally. More and more international locations support eSIM, but not all.

To summarize the solution that worked for me is to delete my existing eSIM cellular plan. Call T-Mobile and provide your EID (found in General -> About) so they can activate the plan on your phone.

This is a pretty specific problem that appears to affect T-Mobile subscribers and a bug in 15.4 and 15.4.1 where delaying installation of an updated Carrier Profile prevents you from installing it later by going to General->About as instructed.

So Apple's "Recommended solution" applies to most others, but not this specific instance. So I wish the higher level members of the Support Community would read the entire discussion before reposting the same information found at Apple Support.

I think i may have been able to solve it. Are you all using an E-Sim only in your device?

I was trying to troubleshoot this issue (spend a night without cell phone service.)

But i was able to get it working again.

1. Have another phone handy cause you will need it to contact you provider (t-mobile in my case)
2. Make sure that you have access to wifi cause you will need it to gain service back.
3. I removed the cellular plan from my account. so that my phone lost service completely. and no service was associated to my phone.
4. Called tmobile from the other phone and asked them re input the EID in their system on their end.
5. waited a few moments and went to add the cellular plan back to my account and then everything starting filling back in.
6. went to reactivate imessage and facetime and it worked with no issue.

Seems like that fixed the problem.

I'm not sure if the people having this problem are using esim or not but this seems to have done the trick and i am able to get and receive imessage and facetime calls again.

I think i may have been able to solve it. Are you all using an E-Sim only in your device?

I was trying to troubleshoot this issue (spend a night without cell phone service.)

But i was able to get it working again.

1. Have another phone handy cause you will need it to contact you provider (t-mobile in my case)
2. Make sure that you have access to wifi cause you will need it to gain service back.
3. I removed the cellular plan from my account. so that my phone lost service completely. and no service was associated to my phone.
4. Called tmobile from the other phone and asked them re input the EID in their system on their end.
5. waited a few moments and went to add the cellular plan back to my account and then everything starting filling back in.
6. went to reactivate imessage and facetime and it worked with no issue.

Seems like that fixed the problem.

I'm not sure if the people having this problem are using esim or not but this seems to have done the trick and i am able to get and receive imessage and facetime calls again.

eSim here with T-Mobile also. Wonder if anything is common here. I did more or less the same thing to get mine working, but time will tell if it "sticks":

Do NOT do this at a time where you cannot speak with your cellular carrier on the phone, either because their support is closed or because you do not have an alternate phone nearby. You will also need your iPhone to be on wifi so it can reactivate

1. Settings > Cellular > Remove Cellular Plan. This will warn multiple times, so make sure you are ready to proceed with the rest of the steps. This will delete settings in your carrier's system.
2. Settings > About. Take note of the "EID" number, you should be able to tap-hold, then Copy it and paste into an email since in my case it was much easier to see on the computer screen.
3. Call carrier and tell them you need to update/add the EID on your phone number. Your carrier will probably make you go through some verification hoops (remember that they CANNOT send you a text at this time since your phone is not on their system; T-Mobile was able to email me a code instead). Give them the EID from step 2.
4. In my case, T-Mobile had me restart my phone, then I was prompted to install the cellular plan. After that iMessage (and Facetime) on the iPhone was able to reactivate on my cell number, and I am getting calls/texts on the iPad as well.
5. Cross fingers.

After hours of trying EVERYTHING removing the Sim and readding it to the phone worked perfectly and iMessage and FaceTime added themselves within seconds.

Remove Cellular Account, Restart the phone, connect to wifi, go to add cellular account and scan the QR code mobile sent you and instantly works.

They really need to address this because less tech savvy people will never figure this out and it was driving me mad.

I have solved this issue with my 13 pro max and t-mobile. My iPhone had an e-sim originally. The tmobile store said they have seen this before and that for some reason the e-sim gets disconnected. They installed a physical sim, reset the network settings, and now iMessage will activate with my phone number as it should.

Good luck everyone!

iOS updates, particularly in USA, sometimes need a carrier update.

If you cannot find the update in Settings, General, About then with the phone on you can either take out the SIM and put it back a couple of times or remove the eSIM plan.

This was pointed out by many posters and the act of removing the plan stimulates the carrier update to be installed.

Settings, Messages, Turn off iMessage

Settings, Face Time, Turn off Face Time

Restart the phone.

Settings, Messages, Turn on iMessage, SMS, MMS

Settings, Face Time, Turn on Face Time

Problem activating iMessage

See If you can't turn on or sign in to iMessage or FaceTime – Apple Support (UK)

I'm on a T-Mobile ESim as well. I've been having the same issue for weeks. I removed my cellular plan and had T-Mobile service added back on. I did this by calling T-Mobile and giving them my EID.

Now, I can quickly activate iMessage with no problems, and everything seems normal. I'll update in a few days to confirm that this resolved the issue.

I too have had the imessages/ios 15.4/e-sim problem since March. Countless nights on the phone with support. Tired of the back and forth between Apple sending me to T-Mobile for support I just sort of gave up (even though the issue was maddening) and hoped that the next update would fix it. Today, after downloading 15.5 the issue persisted so i stopped at the T-Mobile store and had them instal a physical sim card and the issue hasn’t returned since.

jamesbfg wrote:

• Hi all, I've just updated to iOS 15.4 and my iMessage has stopped working. I didn't turn it off but it stopped functioning on my iPhone (still works on my Mac).

I have tried

Restarting (hard reset) iPhone with iMessage off and then turning it on again.

• Turning iMessage on and off again, but I get an error message - "An error occurred during activation."

• I have tired turning on/off Airplane mode.

None of these have worked. A little worried it's a bug in iOS 15.4 as I didn't have any issues before. Any ideas greatly appreciated.

Follow ALL steps here If you can’t turn on or sign in to iMessage or FaceTime - Apple Support

I think it has alot to do with the esims. I had the same problem, i removed my cellular plan from my phone and as i tried to add it back it would not allow me to do so. I went to tmobile and they gave me a physical sim which then added my number back on my phone and then activated with iMessage.

As other’s have mentioned, I went to T-Mobile, for a physical sim and the problem immediately went away. The T-Mobile rep even mentioned that Apple’s implementation of e-sim has caused a lot of problems. It might just be on T-Mobile but just get a physical sim.

Two days ago I walked into T-Mobile. They installed a physical sim and deleted the eSIM cell plan. No issues with iMessage since then. It took 10 minutes and was free.