Peplink with IPTV (Telekom Germany)

I have a Peplink Balance One, which connects to Telekom via PPOE (Zyxel VMG1312-B30A VDSL2 Gateway). All is working, but for some reason the IPTV hangs after 5 seconds (directly connected to the Balance One. Does anybody have experience with Telekom Entertain in Germany or could provide me some hints?