Centos 7 No bootable device found error showing, anyone can solve this?

Hi,
My centos 7 serverwas not responding. When I rebooted it suddenly showing No bootable device found error. Anyone familiar with this centos 7? may be grub issue or something else, can anyone resolve this issue?

I can simply reinstall Os but data important so.

Try to boot from a live USB -> mount your drive and reinstall grub.

Shouldn't be anything too serious if you just rebooted.