I understand that I need to cancel a plan to start a new one, but my paid-for plan has disappeared/expired, I'm currently on a free plan, and I can't buy a new plan.

Instead, I get this error (on multiple browsers) when I click on the plan I want: 

Validate_Dynamic_Params_Failed - Valiate the dynamic parameters failed, some values are not match with the one in signature. 

I can't find any contact info so I'm posting here. Should I delete my account and create a new one, using a new email?  Surely you all want to make sales, no??