Webradio OK, no playlist

I face a persistent problem for which you hopefully can help me.
My Rpi-B worked perfectly with a bunch of radio stations in /WEBRADIO of Volumio 1.51 (with Hifiberry DAC) . Filling the Playlist was never a problem. I made a backup of this and saved it carefully. Now i need this one and whatever i do, /WEBRADIO still shows all stations, but i can not get anything showing up in Playlist, so no sound can be produced.
Is there anybody out there who has a suggestion?
(the same happens with a fresh 1.55 installation)

Thanks in advance.

Have you updated the library after changing the contents?
Go to menu, library, update library.