Based on the diagnostic logs you sent:
1. You have a third party antivirus software (G DATA Security Client) on your primary machine, please make sure to add spacedesk in the exception list to allow incoming and outgoing connection.
2. There are 2 network adapters currently active in your primary machine, Telekom.de 2 (Mobilfunk) and emuench.local(WLAN).
On which network does your iPad device connected?
Also please also try switching the Network Profile to “Private”.
For assistance, please check the chapter “Troubleshooting -> Network Connection” in the user manual https://www.spacedesk.net/user-manual/#item_489.