NamelessMC

this redirect to: 
https://orthyon-mc.fr/forum/error/?error=not_exist

Maybe try a full URL starting with https?

If it still doesn't work, there was a bug to do with local links in topics which has been fixed since the last release; I am not sure if your custom template includes the fix or not.

im using cesium

You can try editing core/classes/Input.php in a text editor, delete all code inside and replace with this new code.

dont work :\