Still working fine here on my development system with latest versions of everything, so it is not an issue with any recent WordPress update.
Most likely a conflict with another plugin that is adding something to, or altering, the Tiny MCE editor. Might have to turn off some plugins one at a time until the PTA one re-appears, to figure out where the conflict is by a process of elimination.
And, stupid question, but are you sure you are in “Visual” mode on the editor? Not “Text” mode, or not using some other visual editor plugin that has its own tab in the editor window?
If you can figure out where the conflict is, I can try installing the same plugin (or theme), to see if I can recreate the issue and look for some kind of compatibility fix.