imac 21.5 late 2012 doesn’t restart after a svram reset

Clearing NVRAM could result in your Mac forgetting where to start up from. To fix this, follow these steps:

1. Hold down the Option key while you restart or turn on your Mac. Release when a selection of startup disks appear.

2. Use the arrow keys to select Macintosh HD.

3. Hold the Control key to set it as the default startup disk, then hit Return.

4. Your Mac should proceed to boot normally.

Hope this helps!

Here's an extensive article on how to use recovery options. I would try internet recovery. If that doesn't work, it's possible you have a hardware problem and your Mac would need looked at.

https://www.techradar.com/how-to/computing/apple/how-to-fix-mac-boot-up-problems -in-recovery-mode-1305641

Sunliner100 wrote:

Thanks for the suggestion, I Try it but no way, the apple with the staus bar appears , then arrive slowly at the end of the bar then stuck there forever.

Asked also apple support who drives me to reinstall OS but again doesn't work.

I starting to be a bit frustrated by this fuit brand....

Then it is probably failed hardware, take it to your local Apple Store or AASP to be professionally diagnosed and repaired.

Attempt a Safe Mode restart and then restart normally.