how did i fixed the problem ?
after contacting the help desk twice, and trying everything (change name, incognito, other browser, wait 24h, disable adblockers, clear cache and cookies, log out-in, revoke the authorization, …)
i tried to create a brand new account. old one in @outlook.com, new one in @edm115.eu.org
WORKED FIRST TRY :clown:

anyway it’s bought, Xbox Elite Series 2 Complete pack, 209,97 €
gonna be delivered in 3/4 weeks