400 Invalid authorization code

I have an authorization website that I created on “wix.com” with that velo stuff and javascript. The first time the user logged in it shows “400 Invalid authorization code” on the “post” request:


The next time the user goes on that website there is no error. The website:


I read that it can be a double usage of the code by twitch given. I didn’t find how to see the exact made http requests on “wix.com

I also found out, that this error just occurs, if the user visits the website the first time like it has something to do with cookies or something like that.