Symptoms

Unable to connect to K2 from K2 Mobile app via HTTPS receiving error: "Mobile services not found"
 

Diagnoses

K2 mobile components supposed to work OOB if K2 is installed correctly and the only thing which is necessary to make it work in terms of server side configuration is proper network bindings configuration and allowed network connectivity to K2 websites from external network.
Most of production deployments require HTTPS binding and it must be configured on IIS side to serve request coming through your external K2 URL (i.e. binding should be either bound to specific host header which match your public URL or set to "All unassigned" in cases when you need to serve request both from internal and external URLs).
When bindings are configured correctly and K2 URL is reachable from external network you should not receive "Mobile services not found" found error.
Another type of error you may face when connecting with K2 Mobile app from mobile devices are the following:

“Request Time Out” (Android)
“WININET_E_CANNOT_CONNECT” (Windows Mobile)

You may observe these errors from Android and Windows Mobile devices while iPhone devices are able to connect to the same K2 environment. These error messages appear when K2 URL certificate used for you K2 HTTPS URL is not trusted on Android/Windows mobile devices. This is security precaution measure and to address it you must have the root certificate of the certificate authority which issued your K2 URL certificate installed on your mobile devices (i.e. your certificate have to be trusted on mobile device).
K2 Mobile app for iOS does not have such requirement and will work with non-trusted certificate, but this may be changed in future versions of K2 Mobile for iOS app.
 

Resolution

For connectivity to K2 using K2 mobile you should have K2 binding properly configured in IIS and network connectivity from external world to your K2 websites must be allowed. K2 Mobile app for Android and Windows mobile also requires use of HTTPS certificate trusted on mobile devices, otherwise you will not be able to connect.