Warning triangles appearing repeatedly in Photoshop CC for fonts that I have activated

I'm using Photoshop CC.

Some months ago, I opened a file Photoshop file that I'd been working on without a problem for a few days and saw that, overnight, all the text layers had acquired warning triangles. I got in touch with Adobe via chat and the chat person spent several hours on my computer fixing the problem. I don't know what the problem actually was.

Then, several months later, the same thing happened. I didn't have hours to set aside to get it fixed but came back to it yesterday and the triangles had disappeared and I worked on the file on and off yesterday for several hours with no problem.

I've just opened the file again and the triangles are back.

The fonts I'm using are all ones that I've activated via Adobe, and they're still activated. I created the file from scratch on this same computer in Photoshop CC - I haven't imported it from another version.

What should I do, please? Chat support doesn't seem to exist any more for individual Photoshop users.