Original context
TB54 I apologize for not being specific. What I mean by "reset" is essentially that you go to your FreeFlarum settings, "Link custom domain" section and replace your current domain withcinstudtest.freeflarum.com. This "resets" (emphasis on quotes) your custom domain back to your FreeFlarum hostname, as it was when you first registered the forum. This step is necessary, so that FreeFlarum can process the new CNAME record.
When your domain is back to your freeflarum.com hostname and your custom domain has a CNAME record pointing to cname.freeflarum.com, you can get back to your FreeFlarum settings and link your custom domain, e. g.: set your forum's hostname back to forum.cinestudia.fr. Once you save changes, and everything went correctly, you should get a browser alert that the domain was set up correctly. If this is not the case, and you get some other message (such as that your domain does not CNAME to cname.freeflarum.com), you might need to wait for a while for the changes to propagate (usually 5 - 10 minutes, but that can vary).
If the link was successful, you should be able to access your forum under your custom domain again (unless there is some DNS or browser cache in place on your side - in that case, try visiting the forum from another device or in private browsing to verify that your domain is indeed accessible by others, and that it is not a cache thing).
