My iMessages on my MacBook Pro have stopped being current as of a month ago. It's now the end of June and it only shows texts from the middle of May.
I noticed my Apple ID was logged out just now (in iMessage on my Mac) so I logged back in, although I never logged out in the first place. So I don't know how long it's been logged out for. Now it's showing some current texts (only from today), but not all that should be an iMessage and texts that were also sent today.