Service won't work on pixel 7

Are there any error messages?   Is the phone new and unlocked?   

Is it under installments on another account?  

It is not new I got it from ebay. It is unlocked. The only thing it will say is no connection .

Okay it's unlocked, but you have no idea whether it's AT&T compatible If you got it off eBay. Do an IMEI check. If it is not intended to work in North America and the correct model number, it won't work here 

https://www.att.com/buy/byod/identify?devicetype=phone

Hi @Goji229 we understand the importance of staying connected on your device. Let's help figure out what's causing this. Please go to our support page to troubleshoot your device and get help, let us know how it goes.

Thank you for visiting AT&T Community Forums.
CrystalS AT&T Community Forums Specialist.

The IMEI is AT&T compatible and should work.

We understand and want to help you @Goji229, please follow the below steps to get the assistance you need.

The Community Forums are a public support option where other users, and AT&T, will try and assist with high level support needs. This means we won’t be able to look into account specific concerns.  To get the help you need for your unique issue, please review our Contact Us page, and choose the best option to reach out to us.  You can call, chat, or reach out via social media, and we can review your specific issue and provide you support.  If you feel your issue isn’t account specific, and can be answered generally, please let us know, and we’ll be happy to help.

Thank you for visiting AT&T Community Forums. 

CrystalS AT&T Community Forums Specialist.

its probably because you updated to the latest April patch and it is not compatible with the ATT network right now, I have a pixel 8 doing same thing.  fix the problem ATT.