Why are my music files deleted from my Fenix 7?

Hi,

I try to transfer my own music files to my Fenix 7. Garmin Express reports successful completion of the transfer. However, there are no files on the watch.

Setup:

Windows 10, fully updated,

GE, version 7.19.0.00

music CD without any DRM

songs ripped from this CD using Windows Media Player, stored as *.wav

transferred to the Fenix watch, as per GE successfully

When I try to play the music, I always get a message that I should first transfer content from the PC to the watch.

Any ideas what's going on or wrong here?

Thx in advance.

HB