I can't log in to the marketplace (but CAN log onto warthunder.com). Tried several browsers and units, cleared cookies, TFA is up and running

It prompts me to log in again, which I do, and I just return to the same screen.
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EDIT: I can log on fine on my phone, but on my desktop neither the steam browser, nor chrome, nor firefox works (with cookies cleared etc)

once you click the relogin button, click log in as another account or something then log in normally

Same thing happens when I use the Another account option to enter my details manually. I get back to the above screen.