Recognizing a Catalog on an external drive

[BSMercer]

I normally work on a PC in LR classic with all images and catalog stored on a external HD but Catalog is also backed up to a folder on the PC. I am in a different location and have a MacBook laptop but when I plug in the external drive and go to the catalog I am getting this message.

Lightroom cannot open the catalog named LR5-2-2-2 locted on Volume "MASTER" because Lightroom cannot save changes to this location.

Lightroom Catalogs can not be opened on network volumes, removable storage, or read only volumes.

I'd really appreciate some help with this problem because I will be using the new MacBook while I am dislocated due to the pandemic. I never expected this recognition problem because I've been using external drives with LR and my PC for years. In finder I can see my files and catalog.

[cmgap]

If   you are running Catalina on your macbook pro you need to setup permissions in your  System Preferences>Security  and Privacy> Files and Folders (and Full Disk Access). You will have to unlock the settings by adding your password then add Lightroom in the right hand column.

[ManiacJoe]

One more thing to check: What file system format are the external drives from your PC?

Earlier versions of the Mac OS cannot write to NTFS drives. I don't know if that is now working in the current versions.

[BSMercer]

Thanks. It seems that the problem is the PC format. 

[Conrad C]

If the file system is the problem, the possible solutions are:

• If it's NTFS, you can get software like Microsoft NTFS for Mac that can let a Mac read/write that file system.
• If you want the drive to be read on both PCs and Macs without extra software, you can use Apple Disk Utility to reformat it as FAT32 or ExFAT.
• If you only need it to be read/written by a Mac, you can reformat it as HFS+.