I ended up just manually downloading each plugin I own from the website and doing offline activation. Works until they get it all sorted out.
I did the same, but can't get any further than my upload of the offline activation request, as Arturia seem to be ignoring it, and haven't bothered responding with the email and activation file I need to complete it. Their "support" is the worst I've ever encountered, and their response times are dire. Having read through many pages of this forum, it's become obvious that this issue has been ongoing for almost four (!) years now, and it's still happening, to some people at least. Abysmal service.
UPDATE : I finally received an offline activation file. Still no joy getting the ASC login to work, but at least Pigments is now usable.