I was able to reproduce this myself on Windows, and I think I’ve identified the problem to be an xTB/conda bug, not a problem with the xTB plugin.
It seems that, for some reason, the Conda version of xTB is not functioning properly on Windows (which has been noted by others), but the actual precompiled binaries available from the xTB GitHub page do function properly. Thankfully the xTB plugin makes it pretty trivial to switch which xTB executable you’re using. Just go to Extensions ⇒ Semi-Empirical QM (xTB) ⇒ Configure... and, after you’ve downloaded the Windows binaries from the GitHub page, select xtb.exe as your binary.