Maintenance for the week of March 25:
• [COMPLETE] ESO Store and Account System for maintenance – March 28, 9:00AM EDT (13:00 UTC) - 12:00PM EDT (16:00 UTC)
Oh, that is strange. Usually when you click in "Web Assistant", they ask for support category, then sub-category. Then you can enter your issue in the "add issue details".
Can you enter an "in-game" ticket? Depending on the reason (like items or quests) you can do that. Try to see if you can use the "help" section in-game. I have used it and it created a ticket for me.