This is a recurring problem. Sometimes, I cannot type text in any of the text edit functions. I can create a text box or bubble, just can't type any words in (or copy anything).
Everything works, and then it doesn't. Sometimes restarting the app or OS helps, sometimes doesn't. It's been happening for more than a year now, on and off, and it is extremely frustrating.
My Mac OS and Adobe Acrobat is up to date. I disabled protected mode at startup and and disabled enhanced security. Nothing is locked.