Problem with "Back Up" in Lightroom

Thank you. The problem has been solved.

This is a problem that has been reported here quite a few times. It is caused by catalog corruption. Lightroom Classic 14 and 15 appear to be more susceptible to it than previous versions, so the corruption could be very old already, meaning using a backup may not solve it. What you can try is this, so far it works for almost all people: Create a brand new catalog and choose 'File - Import from Another Catalog'. Select your old catalog to import. In the import dialog choose to import all photos, but do not move them. This will create an exact copy of your old catalog, but usually without the corruption. The only thing that won't come across is any publishing services you may have. You will have to recreate those. If you synced your catalog then you will have to enable sync for the new catalog. There are some reports that this could cause a problem. Here’s how to solve that: https://www.danhartfordphoto.com/blog/2025/1/lr026-fixing-sync-problems-caused-by-switching-the-sync-catalog

Check the points that show in the error message.

Do you have the appropriate rights to the drive and/or folder in which the backup will be created? The best is you've full access rights.

How to Change Folder Permissions on Windows | V2 Cloud

Do you have enough free disk space on the appropriate drive for backup and on the drive (mostly drive C) for the temporary files?

If this doesn't help, try to reset the Lightroom preferences.

https://www.lightroomqueen.com/how-do-i-reset-lightrooms-preferences/

It's recommended to backup your preferences before you reset the preferences to the default settings:

https://helpx.adobe.com/lightroom-classic/kb/preference-file-and-other-file-locations.html

If this also doesn't help, provide a copy of your 'System Info'. This can be get from the LrC Help > System Info menu item. There's a copy button in the System Info dialog. Press this button and paste the info into your next forum post.