Can't play from any radio station

I have a LMS running on a Linux Ubuntu server and three RPi players with Max2Play software.
Up to yesterday everything was running smoothly; radio stations were accessible.
Since today I can't access any radio station. I get an error message: "Could'nt resolve IP adress for: opml.radiotime.com".
I upgraded from LMS 8.1.1 to 8.1.2 to 8.2, still the same error.

Any idea what's going wrong??

Regards
Rainer