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.
That likely explains your above problem.
what hardware are you uploading to?
Pixraptor, full size unit with suspended IMU. So far have proven to be fully compatible with the design.
I can try other hardware if it would help. I have Pixhawk 2.4.8, MicroPix, PixFalcon, Fixhawk and Pixhawk Lite.
Working now so it must have been a bad segment in the network connection to the ardupilot.org servers or where ever the hex files are stored. I have a real problem getting to ardupilot.org with 2 minute delays in showing pages.