Under Fedora-34, from time to time, Firefox will failed to open Fedora nightly compose finder .
At this moment, Chrome and Vivaldi has no problem open that link, but Firefox failed with:
Service Unavailable The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later. Apache Server at openqa.fedoraproject.org Port 443
It is the same as normal Firefox and Private Firefox.
Normally, sometimes later (hours or days) it will resume normal again.