This message is normal, can you open the console window:
This
And give me the errors?
This is what pops up when I get to “toggle system console” …
Thank u for the patience, I feel a bit dumb with all those questions 
Ok, I think I found the problem. Did you download it on GitHub by clicking the green button?? This not the correct way, because you download the whole development environment with unrelated files.
Instead, download it by clicking in the link in the description on the GitHub page. Then try to reinstall it. You will get a warning saying that it could be incompatible with your version of blender, but I think you can ignore it.
Done with the install, appears on list, but now it looks like this when I try to use it.
( I did got the warning message )
Ok, good news, now I need the console log for the errors, now there should be something
You must disable uv sync:
You didn’t see any error or warning because I didn’t update this part, theoretically you should have seen a warning in the right panel. I’ll update it to display the warning correctly. Anyway, the script will not work with uv sync enabled.
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Oh Lord, now everything is working right, than you so much for all the help. This is literally the best tool I have now and is saving me a lot of work.
Again, thanks a lot 
Un abbraccio
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Oh no, one of the most useful UV editing tool for Blender that should have been built in is not working for Blender 3 !
Developer/Creator, please have mercy !
thanks for reporting, i’ll look at this as soon as i can!
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Hello guys, I’ve ported it to blender 3.1(alpha). It should be backward compatible.
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Thank you, this is an absolutely indispensable tool for Blender.
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