Why have my iPad and iPhone stopped syncing iMessages

Hey guys,

I've been using my iPhone 5 (7.1.2) and iPad mini (8.3) for iMessage successfully for a couple of years now, and all of a sudden the sent messages seem to have fallen out of sync between my two devices. I'll try my best to explain what I mean by this; when I used to send a message, for example from my iPhone, that same sent message used to appear also on my iPad as a sent message but now no longer does so. I have tried turning on and off iMessage on both devices and logging back in etc. but nothing seems to help, I just want it back to how it used to be, as a message exchange can become really confusing if the sent message isn't appearing on the other device's sent message feed.

If anyone has any advice whatsoever I'd be really grateful as many forums approach this problem as if they haven't been previously synced, unlike mine.

Many thanks in advance 🙂