There have been a number of failures which “look like” an apn failure, but may have been partially explained by /e/ support in a French language post translated and referenced here SMS - can receive, cannot send after update to v1.15 - #3 by petefoth.
Searching for related issues on our gitlab, I am really not certain if this https://gitlab.e.foundation/e/backlog/-/issues/7303 is the issue being referred. Sorry not to be able to help more.