Ok… I solved the issue.
adding the :Z to the end of the volume allows the container to access the host filesystem. The uppercase Z means it’s limited to the container you’re running with the command. Lower case z allows all containers to access the folder.
Hope this helps someone… because this was difficult to troubleshoot as there were no real errors that pointed to this.
Thanks for all the help! 
Sneak-peak
My family is not pleased with the workflow of downloading an album from the well sorted beets library, uploading it into the well sorted teddycloud library sorting and encoding, looking for a tag id, searching through the library and having to name the tag…
So thanks to you @marco79cgn and opus2tonie and the great work of the revvox team, I was able to build library2tonie. A docker container, where you mount your library with web-interface, choose a toniebox, put a chip on the box, 1-click upload an album and assign it to the chip last put on the chosen box.
I’ll add a little polish and publish soon.
Cheers
Hi, first of all thanks a lot for the audio2tonie docker container I use it regularly and have only one question. It seems the audio levels are quite low means the kids really use full volume almost all the time and I wondered if it results from the process. Anyway has someone played around or where would I add in some over 100% volume level increase etc
