why the network isn't working after ios10 update?

Reset your Network Settings. Tap Settings > General > Reset > Reset Network Settings. This also resets Wi-Fi networks and passwords, cellular settings, and VPN and APN settings that you've used before.

If that doesn't help, try here > If you can't connect to a cellular network or cellular data - Apple Support

The first place to check is your carrier. Maybe you have an outstanding carrier update to be installed. Check with them about your lack of service.

I am also experiencing this issue on my iPhone 6, running iOS 10.0.1. I have already swapped the SIM card, wiped and reset the entire device, reset my network settings.

Currently, Apple support is sending me to a 'Apple Care technician' to have the HW looked at.

This problem started happening in the morning of Sept. 20th, 2016. I have had two occasions where resetting my 'Network Settings', put my device back on the AT&T network for 5 minutes, then the problem started occurred again, and my phone started 'Searching ...' again, and hasn't stopped.

I suspect this is an iOS 10.0.1 update issue.

I suspect it has nothing to do with iOS 10.0.1. My iPhone 6 is on 10.0.1 and AT&T and I have no problem. And if it really were an update issue there would be thousands of posts about it, and it would be in all of the news media.

Step 1 is to call AT&T and see if they have a network outage in your area.

Step 2 is to see if there is a carrier update from AT&T. To do this go to Settings/General/About and tap on "AT&T". Normally that will tell you if an update is pending.

You can obviously do these in the reverse order.

Lawrence,

Sorry to tell you that's where I started. AT&T escalated my call to Apple after they could not solve the problem with a SIM card swap, Network setting clear, etc.

This is an Apple issue.

I'm having this same issue on my brand new iPhone 7. Typically says "No Service," but will cycle through "Searching" and "AT&T" with 5 bars and LTE - however, even when connected, can't receive calls/messages/data through cell connection.

Specs:

-iPhone 7, 256GB

-iOS 10.0.1

-PC used for iTunes restore: Lenovo x240, Windows 10, iTunes 12.5.1.21

-Carrier: AT&T, Washington DC area

Actions taken:

-4 hours on phone with AT&T, trying every combination of reset/restore/restore from iTunes possible

-1 hour on phone with Apple, walking through same processes; resulted in appointment at Apple Store (that I had to schedule 1 week out...)

Of note, this same issue happened with my girlfriend's iPhone 6 with iOS 10.0.1, but has not been as severe and she normally has a usable cell connection (though her phone will cycle through the "No Service"/"Searching"/"AT&T" status a few times per day). This started after upgrade to iOS 10.

Will post a follow-up after my appointment.

Same problem with iPhone 6s and ATT. One of my friends is also experiencing the same problem. I've been through all the trouble shooting with no success. ATT claims it is working on a fix on their end, but nothing yet.