Ok, had something to upload this morning.
The first two FTPs was using my home wifi and VPN, PM kicked out an an error just after connecting.
The second was on the hotspot, no VPN, and PM didn’t send. Had to abort after several minutes. While waiting, I opened the terminal as was able to FTP into Alamy, and change directories. Hotspot doesn’t seem to block FTP.
The third was home wifi, as normal, and PM sent just fine.
I’ve emailed the file to support, with a note about this thread.
Thanks.