Can't deactivate on failed computer, product not showing under purchased products in account where deactivate button would reside.

I think your "how to" will be here:

https://forums.stardock.com/486311/accounts-and-activation-support-faq#deactivateproduct

Yes I read that article before posting. The product doesn't show up under my downloads either even though it says it should after first activation.

The continue button fails when I press it.

Hello,
Sorry to hear you are having issues. Please raise support ticket using the link below, use the product not receive 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/13

Thanks
Basj,
Stardock Community Assistant