Data recovery: APFS drive not mounting/mounted

My APFS external hard drive is not mounting in disk utility after High Sierra updates, how to repair it so that I can access data again?

"External hard drive is mounting" is a common problem in macOS, this article will introduce two solutions to fix "APFS drive not mounting/mounted" error.

Solution 1: Fix "APFS drive not mounting/mounted" error with Disk Utility

Disk Utility can fix certain disk problems — for example, multiple apps quit unexpectedly, a file is corrupted, an external device doesn't work properly, or your computer won't start up.

Step 1: Open Applications folder, select Utilities and Disk Utility.

Step 2: Select the unmountable APFS drive from left panel, then click "First Aid".

Step 3: Click Run.

If Disk Utility cannot repair unmountable APFS drive, please go to solution 2 to recover data from unmountable APFS drive.

Solution 2: Recover lost data after APFS drive not mounting/mounted and then reformat unmountable APFS drive

Data recovery from unmountable APFS drive requires us to find a APFS data recovery software, M3 Mac Data Recovery is such a APFS data recovery software which can recover deleted/lost files from APFS drive, recover data from formatted APFS drive, recover data from unmountable APFS drive, recover data from unreadable APFS drive, recover data from crashed APFS drive, recover data from corrupted APFS drive, recover deleted/lost APFS partition, recover lost data from encrypted APFS drive, etc. in macOS 10.13 High Sierra/10.12 Sierra and Mac OS X 10.11/10.10/10.9/10.8/10.7.

Tutorial to recover data from unmountable APFS drive

Step 1: Download and install M3 Mac Data Recovery on your Mac computer.

Step 2: Launch M3 Mac Data Recovery.

APFS data recovery software

Step 3: Select the unmountable APFS drive and then click Next to continue.

If the unmountable drive is encrypted APFS, please enter the unlock password as below:

Enter the password to scan lost files from encrypted APFS drive with M3 Mac Data Recovery

Step 4: M3 Mac Data Recovery is scanning lost data from unmountable APFS drive.

Scan lost data from unmountable APFS drive with M3 Mac Data Recovery

Step 5: Select the found data and then click Recover to save them.

Recover lost data from unmountable APFS drive with M3 Mac Data Recovery

After data recovery is successfully done, please select the unmountable APFS drive in disk utility and then click Erase button to reformat it. The unmountable APFS drive will be working again after format completes.