Had exactly the same problem past weeks and also reported the problem to support and got the same generic answer.

Now I notice that something has changed since this weekend :
- before this week-end I got "expired" for all surveys & quick surveys
- now I get "expired" for all surveys but I was able to complete quick surveys

Also I got an email from E-Rewards yesterday indicating that they have waived currency expiration (due to happen may 1st) for me this year.

Still a mystery though..