Have you tried rebooting the NAS, that would be the first thing to try, if that fails then you could try logging into the NAS by entering its IP address into your browser window. If you don’t know the IP address use QNAP’s Qfinder program for Windows or Mac
the NAS default user is Admin and the password is admin (although hopefully you have changed it).
Once you are logged in you will see a series of icons one is the App center if you select this you should see the Sooloos app, ensure it is enabled, in fact it may be a good idea to disable it and re-enable it by clicking the ‘switch’ on the app.
Sooloos wise I don’t believe there is any configuration to do, the NAS should show up automatically as ‘non Sooloos storage’