I've been trying to multi-sell trading cards for days now, and I just keep getting a "Your inventory is currently unavailable. Please try again later." error. It doesn't matter which game the trading cards are for, or what day/hour I try to multi-sell.

I would like to open a Steam Support Ticket, but any time I go through their help section and select "I Can't Use the Community Market" (or whatever the wording is), it just takes me to a help article without being able to open a ticket.