Hi Patrick,
The upload button is going to do an HTTP PUT to your server through Apache, at least for collections tied to a POSIX storage gateway. (I’m not sure if Globus uses other HTTP servers for different Linux distributions.)
The upload will show up in the Apache logs, which on an Ubuntu instance is at
/var/log/apache2/other_vhosts_access.log
If something went wrong, you’ll probably find a hint in the error.log file in the same directory.
I was able to upload a 5.5GB file from my Mac through Safari to a GCS DTN running on Ubuntu 22.04LTS. I have old memories of 2GB or similar limits on HTTP PUTs and GETs, which may not be accurate.
Hopefully this gets you looking in the right place for troubleshooting.
—Rick