I'm told by support that this has occurred to others, but I couldn't find any reports when searching.
I have one character who, on creation, I set the name - both the short name and the first/middle/last names - but on completing the creation process, the short name was the original generated name rather than what I'd set it to. I wanted to fix that, and was willing to spend the US$3.50 for a rename token (though I haven't yet).
When I went to the character and pressed the "Rename" button, though, I got this:
Clicking the "Free" button dismisses the dialog, but does nothing else.
Interestingly, yesterday for a very brief time, I got this dialog:
As you can see from the screenshot, though, I didn't have any Zen available. So I exited STO and bought some Zen so I could purchase the rename token, but when I went back into the game and tried the Rename again (thinking it was fixed), I got the blank screen again with the "Free" button. The time at which I received the correct rename dialog was approximately 8:50am PST, July 6, 2023.