Further, try Mac external hard drive recovery software as a last resort.
It will further resolve errors like – Though helpful, FSCK isn’t the sure shot method to repair the corrupt external/internal hard drive.
You might need the help of a professional external hard drive recovery software for Mac.
After wrangling with a broken EFI partition on a Mac recently, I personally found the fastest and most foolproof method of fixing the EFI partition and to get the Mac to boot again was .
I fiddled with the other options, but ultimately just reinstalling Mac OS system software did the job for the situation I encountered.
It is not the most elegant solution, but reinstalling Mac OS system software should repair a broken or damaged EFI partition, or if one is missing somehow it will recreate one in the OS install process.
You can reinstall Mac OS X using any of three methods: using a bootable disk, using Internet Recovery, or using normal Recover mode, which approach you will probably depend on Hopefully you have made a full backup of the Mac before the EFI partition failed to begin with, otherwise you should complete a backup before attempting to reinstall Mac OS system software.
Finally, something else to keep in mind is that sometimes damaged or broken EFI partitions can be an indicator of an impending disk failure, or some other problem with the hard drive.
If you suspect that may be the case, you may want to attempt to repair the drive through Disk Utility and run Apple Hardware Test on the Mac to see if any hardware related disk errors appear.
Stellar Data Recovery Professional is a sophisticated application to scan and recover your APFS or HFS drive.