Bambu Studio - send to Octoprint (in other network) - bug?

In preparation of the arrivel of my P1P I already installed Bambu Studio (1.4.0.18) onto Windows 10, locale=german. I was quite pleased to see that you provide a profile for an Ender-3 (V2) which I gladly used and modified it for my Ender-3 Pro which is controlled by an Octoprint instance.
For several reasons the Octoprint is located in another network segment (to which the computer’s network has full access, though). I set up Octoprint as a target with its IP V4 address and provided a valid API key. The test function says “Connection to OctoPrint works correctly”.
What I cannot achieve is to actually send a sliced plate to Octoprint. After sclicing, the button stays greyed out (different than the “Export G-Code file” function).
Is this behavior still work in progress? What else is the reason for sending not working?
EDIT: Using the same computer, Prusaslicer is perfectly able to send to the same Octoprint instance.