Hi Paul, glad to read you!
This is the XML that going up from JSitemap: https://prnt.sc/qfH1NTmv8t3W
As you can see, there are not the parameters that it need to be correct, as is the reason of this ticket.
This is the reply from JSitemap assistance (I've boxed the replay that are related to this issue): https://prnt.sc/eRROOYQk6V0f
If you need other, tell me promtly. I think that you have the user and psw to enter in administrator side. Pocha is installed to view and modify the files on the root direcory, in which you'll find the sitemaps.
Thank you!