Issues with mounting external drive when upgrading to OSX27

The error com.apple.DiskManagement.disenter error -119930868 typically indicates a hung background filesystem process (fsck) or a third-party kernel/security extension conflict preventing proper volume mounting.

If you have 3rd party ‘protection’ software installed, that may be the problem. For example, ESET has been reported to prevent external drives and memory cards from mounting. Such 3rd party system ‘helpers’, ‘cleaners’ and ‘protectors’ do more harm than good. In fact, such products are completely unnecessary for macOS and the only ‘good’ (if you want to call it that) they do is to put money in the developers’ pockets. For the user, they offer only harm…and if that is limited to harm to your bank account, then count yourself lucky.

see if the problem is present when you boot in safe mode. That process performs some system cleanup and clears caches, and also disables 3rd party extensions that may cause problems.

Start up your Mac in safe mode - Apple Support

If that does not correct the issue, test in a new user account. A newly-created user account will have all settings at default, and if the issue does not occur in that new account then it provides guidance on what may need to be changed to correct the issue.

Add a user or group on Mac - Apple Support

Once the testing is complete, the new account can easily be deleted.

Delete a user or group on Mac – Apple Support

Those steps will help to isolate the problem.

It might help to download and run EtreCheck, written by a long-time forum member. The free version is fine. Post the full report using the Additional Text button. No personal information is revealed. 

Solved: USB drives detected but not mounting on Mac — ESET Device Control rule

I’m sharing this in case it helps anyone experiencing a similar issue.

On my 14-inch MacBook Pro with an M4 Max chip, USB storage devices were detected by Disk Utility but would not mount in normal macOS operation. The problem affected different file systems, including NTFS and FAT32.

One drive produced this error:

com.apple.DiskManagement.disenter error 49153

During troubleshooting:

• The USB drive worked on another computer.
• A FAT32 drive mounted successfully in macOS Recovery.
• The drive worked across all USB ports during the successful test.
• Reinstalling macOS without erasing the internal disk did not resolve the issue.

The cause in my case was an enabled blocking rule in ESET Cyber Security’s Device Control settings.

The rule applied to all device types and all users. macOS could detect the drive and its partition, but ESET prevented the volume from mounting.

What fixed it:

1. Open ESET Cyber Security.
2. Go to Protections → Computer → Device Control.
3. Open the information/settings button → Rules.
4. Check for an enabled rule that blocks all devices.
5. Uncheck Enabled for that specific rule and click Accept/OK to save.
6. Disconnect and reconnect the USB drive.

After disabling that rule, my USB storage devices worked normally again. I left the antivirus, real-time protection, and firewall enabled.

No disk formatting, kernel modifications, or further macOS reinstallations were needed.

This error can have other causes, but if you use ESET and your drives mount in Recovery while failing in normal operation, check the Device Control rules before attempting more invasive repairs.