Update option disabled in Studio 2015

Hi

I face a strange situation on one of my training workstations. Studio 2015 SR2 is installed and working fine, with one exception: the option to check for updates is greyed out.

This is how it looks:

The same applies to the setting in "Options":

I have tried several corrective actions:

- reset the Usersettings (delete the file)
- launch Studio with admin rights
- repair

I also checked if all plugins, including system plugins, were enabled. They are. 

All these actions did not solve the problem.

The strange thing is that if I reset the options to default, it does enable the automatic update:

... but still leaves the setting greyed and inaccessible.

Has anyone ever experienced this?

What could cause this to happen?

Walter