Running OS 10.15.7 and still nothing from the Rename menu item.
It might be worth note that ‘Save As’, that “relic” of a simpler time, a vestige before the enlightenment when Apple got silly, you need to hit the option key when you pull down the menu.
I personally love “Save As” and thank goodness if you know the ‘trick’ you can see its ghost reappear.
I too find that ‘Rename’ does not work in the latest edition of Pan X. I was frustrated but found a workaround. Rather convoluted of duplicating the file and renaming it in the Finder or Saving a Duplicate within Pan X.
But now I know the trick. OPTION KEY.
Brings back Old Memories.
I don’t know if this still works, but this article shows how to add the Save As command back to the menu (it definitely worked as of Mojave).
And for what it is worth, the non function of Rename continues in macOS 12.0.1, v b25.
If anyone cares about the Rename menu item, you can vote for it in BitBucket. 
macOS 12.4
Pano 10.2.0.b26
Definitely still works fine for me. I had just used it yesterday.
Since it is a system process, there must be something wrong with your system. An incompatible application? Try it in Safe Mode.