WOW! Thanks so very much!
It worked for me also by installing the Plex App for Windows
Here I could login, go to the Server-Settings, Live TV & DVR and finally was able to scan for the channels (because here the different regions (frequencies) for Germany showed up in the old DVR layout). The postalcode (PLZ) for EPG is entered AFTER the scan in this old version on DVR-Setup (for me I took EPG "Horizon TV (352 channels)). Worked perfect!
My Setup is the newest Plex server (Beta) with Plex Pass on nvidia Shield TV (2017) with the Hauppauge WinTV-dualHD and Vodafone Kabel (unitymedia) in Germany, Baden-Württemberg
So, a BIG THX again for the clue! 
