After some research, it seems to be a recent problem that affects a lot of ppl : https://www.reddit.com/r/OperaGX/comments/1xda7nn/netflix_not_loading_only_on_gx_browser

Got exactly the same problem few days ago... And now I can't even access the website, it shows an error 500 immediatly. But it works on a private window.
Tried to delete cookies but the problem persists..