Hello Melissa841
Thanks for posting in the community! Sorry to hear about the library issues, but I'd be glad to assist!
In order for the music library to work, the computer needs to be turned on and running.
So if you're attempting to access the library from your mobile device while the computer is in sleep mode or turned off, this will populate this error.
I would recommend making sure the computer is turned on, and in the energy saving settings, make sure that "put hard disks to sleep" is disabled.
The other option is if you don't want to have you're computer running all the time, other users have had luck using a NAS drive like the Western Digital My Cloud. This is a hard drive that connects to your router so you can access your library all the time from all your devices with the SoundTouch App.
Warm Regards,
Tony - Community Support