Then back to the forum again, and I'm logged in.
No, when I'am going back from WordPress to the Forum.When you return to WordPress are you logged in?
The WordPress plugin Query Monitor is enabled now. But I have no experience with it. I do not know where to look at. @LPH has my login if you want to look somewhere.Can you install the WordPress plugin Query Monitor and see if the cookies are being set properly?
For the time being, I solved the problem by turning off the CDN connection
KeyCDNWhich CDN are you using?
NoAre there settings regarding cookies?