I had the same experience, Julie. Producteev shut down and I've heard of no case where a user has successfully accessed the app or exported data beyond last week. Most of us are simply monitoring this forum and hoping.
So sorry for your pain.
Did you hear that Producteev is back online for a limited time? I was able to login and export all my tasks. I recommend you do the same ASAP, and definitely before 18 June.