You are able to see the tracks, adding them on the playqueue, but you can't play them.
This issue is due to your firewall parameter, you will need to allow Spark on the configuration of your firewall.
- On your Windows PC, click on the windows logo
- Select "Parameter"
- Select "Internet and network"
- Within the tab "Wifi" at the bottom of the option list click on "Windows Firewall"
- Then on the left panel "Allow an application or a feature via the Windows firewall".
- On this new windows, click on the button "modify the parameters"
- Tick on all Spark instance available on the list
- Click on "Ok" to confirm this parameter.
Note: This steps above are for Windows 7, 8 and 10