Cannot unlock a paid off device "network error"
I have two phones from that account, an iPhone 8 and an iPhone XS. I was able to unlock the iPhone 8 just fine using the device unlock portal at att.com/deviceunlock/. The iPhone XS results in a generic error: "Oops! Looks like we're having network difficulties. Try again later." Like many others have posted, simply waiting until later does not work. There is something wrong on the back end and nobody I've called at AT&T on the phone has been able to help me. They keep opening cases and giving me resolution dates with no real explanation as to why the device cannot be unlocked. The account has been paid in full and there is no remaining AT&T Next balance. Out of all the times I've unlocked devices, this is the only time this has happened.
Can someone please look into this for me or at least explain why this happened? I cannot see any logical reason why I cannot unlock a device that I own free and clear.