Redeem Code page says my account is not linked, but it is.

I'm signed into the exact same account on the mobile game settings as the one I'm using on my browser, but I keep getting this message. I can verify this because when I click "Manage EA Account" in the settings, it takes me to the very same account online. 

I've tried linking Facebook and Apple as well, but still get the message and cannot redeem a code. Does anyone know what I can do or how to get help from EA?