So I bought a copy of the 2025 Premium Edition on Steam, but I already have ESO from when I preordered it before it first came out, so after installing, I chose the option about having an existing account. It wants me to enter the activation code that the game client is giving me into the website. But each time I do, I keep getting an error.

Error: Activation Code not found or has expired, please generate a new one and try again.

The activation code is only a few seconds old, so I doubt it expired. What's going on? I tried it 4 times, no luck.