Nextcloud with iframes

I would like to set up a rerouting via my domain supplier but this rerouting is in an iframe.
And when I reach the URL of rerouting, thus which is redirected towards the URL “normal” of my domain, nothing displays, no errors.

Example :

All of others existing reroutings URL work.

Is there an incompatibility with Nextcloud and iframes or is there a particular configuration to be made so that work?