Compatibility of Zoom Meeting SDK with Zoom X (Deutsche Telekom) - Error 3000

Dear Zoom Community,
Our app successfully integrated the Zoom Meeting SDK for Windows.
Regular Zoom meetings work fine.
A few customers are using “Zoom X”, the version powered by Deutsche Telekom (see Zoom X powered by Telekom: Wie Zoom und die Deutsche Telekom Kommunikation neu definieren | Zoom).
They can successfully get an authentication token via the Zoom Meeting SDK and schedule a meeting, but when they try joining a “Zoom X” this meeting or another Zoom X meeting, an error occurs: “Invalid meeting ID error 3000”.

Is this because they need to be on a Deutsche Telekom dedicated network, or because the SDK is not compatible or it requires a proxy / different configuration?
Thank you