Media Server suddenly lost!

Volumio Version: 2.878
Hardware: Volumio Primo
DAC: TEAC UD-501

Hi at all!
The hardware was correctly installed, and music was played allready from the media server for hours.
All was fine.
Today I wanted playing music again, startet the software on Windows again, but it says “no items”.
Best of all: the last title displayed is still able to be played!!!
The NAS is “on air”, “on line”, and everything is fine.
But there is no media server in the Volumio Primo!

Anyone suggestions for killing this bug?

Supplement:
The volumio primo displays the NAS as the basis for a media library!