I read some issue. There are a same problem.
But my case, I don't sure. What is the reason? I cannot access in Adobe stock but can sign in at Fotolia.
So, How should I do?
You had created 3 separate accounts at Fotolia. Only one of which was validated. It's likely you synced to one of the invalid accounts since the email address was the same. This would prevent you from accessing the contributor portal. I have deleted the two invalid accounts. Try accessing and syncing the contributor portal to your valid account now.
Since you don't have any existing content at Fotolia, the easiest course of action may be to create a new contributor account at Adobe Stock from scratch. You won't have access to Fotolia this way however.