Can’t update, find update on download page

As the title says. I cant update the ‘Groups Restrict Categories’ plugin. We had it for years, I can still see the order in my account, but I cant open it, and the download page is empty. And on the site we have this installed, you can check for updates via the automatic ithingx updater, but nothing happens, WP itself says there is an update, but it can’t update it.

Any help would be welcome, as the plugin seems to upset some other things in the site.