Spencer Desktop is build on top of Electron, a framework to build desktop applications with web technologies. The frameworks supports proxy configuration out of the box and is documented here:
Several options are available to handle your proxy scenarios. Pass this information to your packaging team, so they can properly configure the setup on your device fleet.
If you're experiencing issues with your proxy, you can leverage Spencer's build in Chrome devtools Inspector.
Open up cmd and set the environment variable SPENCER_DEBUG
Execute the command as you/your admin configured it with all flags as mentioned in your start menu/desktop shortcut
You should see Chrome devtools opening together with Spencer, the network tab most probably will help you investigating what is failing.