How much free storage space do you have on your iPhone? (Settings > General > iPhone Storage)

How much storage is Messages using on your iPhone. (Settings > General > iPhone Storage > Messages)

In Settings > Apple ID, iCloud… > iCloud is Messages turned on or off?

On your Mac in Message > Preferences > General what is Keep messages set to?

On your Mac in Message > Preferences > iMessage > Settings is "enable Messages in iCloud checked (✔)?

If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein