grey screen stuck boot

I'm facing a problem for weeks. Today I gave up and and came here to ask some helppppppp... I'm a system analyst I since some days ago I'd trying to solve an error that makes the Xamarin Mac Agent to not connect my Visual Studio and my Sierra Hackintosh. Looking for a solution to my problem, I...

Hello, My hackintosh has run smoothly for a year or so until now. I switched it off and on again at the mains as FCPX wasn't opening and now the computer itself won't start. Following the grey screen with apple logo it would usually go to desktop but instead it is going to a blank grey screen...

Please help me! I can't boot into os x after I restarted my machine and it installed updates. It just gets stuck on the boot screen and a 'no' 'restricted' sign appears (circle with a line through it) How do I fix this? Windows 7 boots fine Machine was built by a friend who can't help me till...