Unable to update 10.4 in my Apple Watch 10.4 over 50% of preparing stage

Happened to me as well (Watch 9); stuck on... Preparing.

Steps I used to correct: {At this stage, download of watchOS has occurred solely on the iPhone, but Install to watch has not yet begun. BTW, it certainly was not an iPhone storage issue; I've got about 80 GB free.}

1. Did a shutdown-restart of of iPhone (13mini) &
2. Shutdown-restart of watch. {I'm not sure if these 2 steps were necessary.}
3. Last step: In Watch app (iPhone) -> General -> Storage -> watchOS 10.4 download is there -> Deleted watchOS 10.4

Upon completing the above, navigated (Watch app) back to General -> Software Update & started Update a 2d time. ...Update completed normally.

This issue is the 1st time I've experienced it (including all my previous Watches); I've no idea what's the cause. But at least, the above steps was a reasonable correction. And if such happens again, I'll know how to proceed (rather than waiting more than 2 hours, being stuck on Processing).

I was stuck in "Preparing" step for a few hours, too, while trying to update an Apple Watch SE. Eventually, I tried unpairing the watch with my phone, then repairing the watch with my phone, which required downloading the update to the watch again. The update stalled in the same "Preparing" step again, but started to make progress after 15-30 mins, and verified and installed after another 30-60 mins.

I ran my watch down below 50% then but it back on the charger and when it got to 50% or better it installed the 10.4

I shut down both my watch & phone and then powered them both back on. When they came backup, the storage on the watch didn't show that there was an update and the software update section looked like it was ready for me to start the update. Howerever it almost immediately went right back to 60% ish preparing. At that point I went into storage and saw the ~1.06 GB storage consumed by the update of storage and deleted it. Now it started a new download of the software and is taking 15 ish mins to download the update to the watch and I think is going to work and update my watch. We'll see. Thanks for this guide.

i was stuck on preparing for hours. Had my watch and my phone on chargers next to each other. I was told to keep them next to one another. I followed the steps listed by the original poster. Left my watch on the charger and took my phone to the bedroom and it started to finish. Trial and error I guess.

I'm having the exact same issue as you but with a series 9 watch. Just finished a full return to factory settings, reboot, and a re-paring with i phone all with Apple Support on the line. The update progressed to preparing again and stuck at around 60% on the progress bar. This was probably the 4th or 5th try today. My wife's series 9 updated perfectly this morning, same internet service in the same room of the house. Support said the only fix might be a factory flash software update which involves sending the watch to apple.

I have Apple Watch 9. What I did finally after threes days trying, I shut off my watch and restarted it. The Apple Watch should be charging until it updated. Wow and Done.

I had the same problem with my Series 7. I hard rebooted both the phone and watch, and was stuck at "Preparing..." for a long time. Then, it finally started making very, very slow progress, and is now complete.

Thank you,

First my watch battery drained overnight. They suggested an update. There was no red 1 by the watch app. I opened the app and there was an update, but it was stuck on preparing. I spent so much time going through all the steps of turning off and on the phone and watch and waiting for the app to download. Unfortunately it was still on preparing for what seemed like an eternity. I finally found your suggestion and it makes sense. So I am guessing the auto download did not fully complete and it was stuck. For what ever reason the problem occurred you have demonstrated yourself to be a tech genius!

Again thank you soooo much pbGuy!

Auto update failed overnight, so I spent most of a day doing all these recommended fixes...still no update. Did all the restarts, new downloads, etc. & let it try overnight again...still "preparing". We need an update to make updates work.

It took about 30 minutes to complete preparing step iPhone 15 pro , then moves on.

I let my "preparing" run all night. Still stuck the next morning (i.e. today, Mar 7). I also reset the watch, rebooted the iPhone 15 Pro, etc. and no joy.

I attempted again, for about the umpteenth time, and it finally made it past the "preparing". Hoping it will complete the update...

I let preparing all night, about 15hours. it still stuck. Rebotted my iPhone 11 nothing worked.

Same here watch 7 finished next day

The watch 8 doing same thing as yesterday … preparing