Sync apple messages between devices I'm a novice user FYI. My messages used to be synced so that the conversation kept going on iMac iPhone and iPad mini. Then perhaps after a trip to Alaska it stopped doing that. I'm not 100% sure if that's when it stopped. I've noticed that my iBooks content syncs between phone and iPad but not iMessages. This is very inconvenient. All three, actually I have 2 iMacs so 4 devices are with same Apple ID. THANKS!
Check if you have the devices under settings/messages/text messages forwarding, and enable all the devices you want to recieve/send messages from. Even if you already enabled it previously, you might of renamed the device, just check if the device with exact name is enabled.