Can't send license back

Well, the subject says it all, I guess. I've been trying to return a license so I could install Trados 2021 again (after it stopped working alltogether without any apparent reason, so bravo again for such a great product), and now I'm stuck here. Thank God I have a second main device to work with, otherwise this would be costing me quite a bit of money.

But enough, I just wanted to know what to do next, since SDL offers no support whatsoever and their website keeps telling me that "there's been an error" or something.

Thanks.