My 0.8.3 has different languages.
I don’t think you have to pay again, I think you select “already paid” and re-download.
I’m not an expert with problems, but maybe remove FZ, search for left behind FZ files and remove them, then restart PC and try again.
Maybe turn off anti-virus and re-download and install FZ.
Maybe change the language in WIN10 and install FZ.
Other than that I suppose you have to post an official bug in FZ Github - I don’t know how to do that -.
They are under staffed here and we are just volunteers, and the guy that might know only turns up once a week because his internet is broken.