Unable to access most tickets

I need to reply to issue number 63809, but it didn’t accept a response via email and for some reason it and almost all other ones I’ve ever opened do not show up under “my activities” on the support website (while one existing ticket does appear; I am in fact logged in.) Now it’s telling me it’s going to close the first-mentioned unsolved ticket because I haven’t responded to it. Problem is, I don’t actually know how! If I try to cheat it and just stick the ticket number into the URL in place of another ticket’s link, it tells me “oops, the page doesn’t exist.”

What can I do?

If it matters, I exited the Insider program a little while back since I estimated not having any more time for it; I’m not sure if that would have anything to do with my ability to see tickets or not. I re-entered it again to see if that fixed this, but it doesn’t seem like it did.