Photos in messages won't load

A few months ago, I received an alert that my phone was running low on storage. It suggested that I optimize.

I did that.

Now every photo/video that was sent in a text message before that is a blank box that says "tap to download". When I tap, either nothing will happen or it turns into a white square with a question mark.

Some of those photos I really need!

Does anybody know how to fix this??