iMessage waiting for user to accept

same problem. Used to work. Used to be able to hit the spacebar and see the photo large, too. Then it got stuck on one picture and everytime I hit the spacebar - i only saw that picture no matter which picture i hit the spacebar on. I restarted the computer and now i can't hit the spacebar, download any pictures i receive or send any. It just keeps saying "waiting for (number) to accept in the file transfers. The other person on receives a "downloading" but it never starts downloading on their end. Just says 0 bytes/997kg. (or whatever the size)

I tried a few suggestions from other posts. My IMTransferAgent doesn't show up in utilities activity monitor. I don't know how to open ports. None of that makes sense to me. One cool thing was I figured out how to receive other messages from non iphone users on my messages app. That was cool.

Hard core but, if it works, bully for it! For future reference here's how you might be able to get back your messages if you have latest macOS. Enable Messages in iCloud in Messages Accounts settings before you blow away the messages library. Give it time to upload. I think there should be a progress bar at the bottom of the conversations list column. Once it's done or even if it had already been enabled, make absolute sure it's done uploading by clicking on the Sync Now button which should at least momentarily turn to dim, static gray. When it comes back to live black and white, it's done. Now disable Messages in iCloud and give Messages time to communicate that switch to iCloud. Then quit the Messages app (don't just close the UI window), hard-core blow away the messages library per NovaProd's post, open the Messages app and re-enable Messages in iCloud and go from there. Maybe a long shot so, like you said, one should back up the messages they want to keep one way or another before hand.