[PC] Mass Effect Online Access Error in Multiplayer Mode

I just reinstalled ME3 after multiple years and tried to enter multiplayer, which I have played for hundreds of hours!

But instead of getting to the MP lobby, I—like many other people—am suddenly informed that I'm lacking some "online pass" (see screenshot). In the main menu, there's also a button to buy/redeem such a pass (see screenshot), but when I click it, I just see the same screen like when I try to enter multiplayer.

I tried the usual and recommended remedies already, like reinstalling the game, repairing the game files, deleting the license files, clearing the EA apps cache and Windows Temp directory, but nothing helped.

And of course I contacted the support. It is not helpful, to say the very least. I got into chats with multiple so called "agents" who clearly weren't human and gave me no indication whether they can solve this problem or not. Frankly, I'm not even sure the AI bot understood what the issue is 😂. Instead, after a few messages they just ended the chat, the ticket status was set to "player not available", and that is it. I can't eve re-enter the chat. What a middle finger to the customer.

And apparently this problem isn't even hard to solve for support (see linked discussion), which makes this experience all the more frustrating.