If your Mac starts up to a circle with a line through it - Apple

A circle with a line through it means that your startup disk contains a Mac operating system, but it's not a macOS that your Mac can use. 

Apple locked my Mac Pro

why does it show a stop sign - Apple Community

Mac OS install on AMD Ryzen (VMWare) Opencore

Startup issue. PLEASE HELP - Apple Community

2010 Macbook Air failing startup - Apple Community

My computer is completely damaged - Apple Community

Mac OS install on AMD Ryzen (VMWare) Opencore

Startup issue. PLEASE HELP - Apple Community

Did Apple block HS installation for 2018 MBP ?

Mc book pro 12 - Apple Community

Help me regarding issue 2106F when I trie… - Apple Community

My iMac doesn't start and shows a blocked… - Apple Community

iMac won't completely start up - Apple Community