I was also suddenly unable to login to my account.
I have been a customer since 2012, and my account was started with a email-address that no longer exist, a few years later I changed the email-address on the account.
When I tried to login with my old email-address I was able to login to the account, and change the email-address again.
Hello,
Sorry to hear you are having issues. For any account related issue, please raise support ticket using the link below, use the "Ask a Question" option. Include all information details. Remember to record down the ticket number for future reference if needed. Do not raise multiple ticket, that will make your ticket back to the end of the line. Send once and wait. Ticket will be answer by the order they send in.
https://stardock.atlassian.net/servicedesk/customer/portal/4/group/14
Thanks
Basj,
Stardock Community Assistant