The first thing to check is to make sure you aren’t trying to download FOUS data, as it doesn’t exist for Europe (of course, there could be some other issue, but that’s what occurs to me). Is this error still occurring? Can you post a screen shot of WXSIMATE so I can see how you have things set up?
This has happened a couple of times in the past and I have uninstalled WxSim and reinstalled it.
I coped out my config files before and the previous forecast files (wxf files) and once reinstalled, I just copied them back).