There was new code pushed out on Friday that affects the Alpha language version, with the effect that no matter what you do, such as clearing cookies or using a different browser, non-English languages will fail. The only solution is to say “no” when the bar pops up asking if you want the local version, or set the browser locale to English to never get the choice to opt-in to your language.
There is no ChatGPT-specific OpenAI staff here to tell us what they did, say “sorry”, or apparently even read a flood of messages about this problem.