In tryng to troubleshoot a problem with gimbals I needed to install an older version of copter firmware. ALthough I can freely install any version of 3.4.4 I can't install any version of previous software. Mission Planner times out trying to get any older firmware. I tried the lastest an older versions of Mission Planner. It appears to be the server that the archive versions are located on.
Also the older version of firmware appear to be deleted from firmware.us.ardupilot.org for a manual download.