transfering iTunes music to Garmin fenix 6

I am having problems copying my iTunes music to my Garmin fenix 6. I can see the albums I want to share in the Garmin Express app, but each time I try to 'Send to Device' the process fails.

It makes no difference if I create a playlist or convert the iTunes files to ACC and then try to send those, the application process still fails.

Does anyone know what the problem could be?

I have also asked Garmin if they can solve this issue.

Thank you