Signal issues

A friend of mine uses IOS. He has a version of signal 7.72.2. The issue is that he got an alert that signal would stop working the following day. (This happened 30 April)

"This version of Signal expires tomorrow. Update to the latest version."

The thing is, he went into the apple app store, updated it to the latest version (7.72.2) and still, he seems to not be able to use the app properly.

Now he can not send texts, only receive and I simply don't understand why because he did update to the latest version within the app store.

How does one fix this? Any suggestions?