Unfortunately, is not uncommon for websites to probe the browser and/or OS that you're running on, and refuse to work under the pretext that "your system doesn't support it".
Normally, though, you should see an error showing up about it, something like this:
The fact that it's refreshing every so often is most likely an issue with the site. Maybe you have an ad-blocker or something around those lines installed? Either way, definitely reach out to their support to ask about this issue.
Piece of advice: don't mention the OS that you're using, and say that you're using Ubuntu if you're asked about it. In reality this probably makes no difference (web standards exist for this reason), but they'll use it as an excuse to get rid of you quickly.