Can you share the exact error message? I was actually just dealing with such a problem, so if the error message you got was the same as mine, then I think I know the issue.
Incognito/InPrivate browser tabs always use a clear cache and no cookies, so they are definitely a reliable way to access the siteIt's also possible to clear the cache of a website in specific if you use the "f12" menu in your browser. You click f12,...
Yep, I got it too. Although i'm happy with my current plan so I wouldn't switch to it personally. I think it only works if you switch out of your current plan, at least based on the wording.