Issue with Hybrid Azure AD join of Windows 7 devices

Question

Any idea why Downlevel domain-joined devices is disabled while trying to enable Hybrid Azure Ad join in AD to connect the check box for Supported Windows?

Answer 1

Usually, if you are not able to enable a service it means that it is not supported by the system. 

I think you should go through the steps to enable Windows downlevel devices from the Microsoft blog and make sure you haven't skipped on any of them. 

If the problem still persists. check if you're using an updated version and system for the same.