Hello all,
I also have had issues with the messages app, same as everyone else here so I won't go into the laundry list of 'fixes' that I attempted, the same as everyone else here. I contacted Apple Support a week ago to see if they could help. Of course, the person I spoke with also had no idea what would cause the issues because he'd not spoken to anyone else about it and it was new to him (yeah right). I told him to read the message boards because this was a widespread problem and I was shocked to hear he'd not already gotten requests for help. Anyway........whatever. He asked me to do a little troubleshooting, to which I said I had already done all the things and I wasn't going to drag it out by going through his list of fixes. He then forwarded me to a specialist. Long story short, she ran a program on my phone to get data analytics to send to the engineering department, along with a screenshot of my Iphone storage. She said she'd get back to me by today. Well, my storage was about 3/4 full and I wondered if maybe my messages had too many large attachments (pics, videos) this past Tuesday I reviewed them and deleted a bunch, and I mean it was a lot, of videos and pics I had sent via text message over the last 4 years. Messages app still didn't work. Until Wednesday afternoon. All of a sudden, now I receive and can send messages! And the messages are forwarding to my iPads as well, which I was also having issues with. No issues since. I haven't heard back from support yet today. Not sure if I will. But at any rate, its working as it was before. I don't know if engineering was able to do something on their end without me knowing, which I don't think is possible since she had to get my permission to access my phone to do the diagnostics. But maybe it was my messages storage being overloaded with large attachments. I would suggest trying the same thing, maybe its as simple as that. I noticed today that I have a TON of storage on my phone now, as in I'm only using 1/3 of the total amount. I apologize for the long message, but I hope this helps everyone and if you're still having issues, just call support and tell them you need to speak with a specialist.
Good luck to all, this is absolutely frustrating and I'm hoping I have no further issues. I will report back if I do.