Service Unavailable

Today I have updated .net version on the server, after that when I open HC login page it gives error " Service Unavailable ".

Service unavailable identicate that .NetFramework is failing in the IIS, verify this

Go to IIS > Websites > properties > ISAPI filter ::: You will see aspnet 2.0 filter if it is showing in RED down Arrow. Then Remove it and restart IIS

Check if HC website is running under aspnet 2.0 version
Go to IIS > Websites > Hosting Controller > Properties > aspnet tab ::: Make sure .net 2.0 version is enable.

If above suggestions didn't help, then follow this

Open command prompt select path
C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727

execute command
aspnet_regiis.exe -i

Hopefully this will helps to resolve the issue.