P: Updating to version 9 but my catalog from version 8.4 is incompatible

Try a cold reboot, worked for a couple  in the Adobe Support Community. No reason.

I’m having the same issue. Abode is of no help.

Im having the same issue updated to Catalina 10.15 then upon opening Lightroom got message about catalog being incompatible and have to choose a different catalog.  All my files I work with are on an external drive, I noticed that the drive is now handling file paths different than before.  "volumes" is missing before the drive location.  It is also showing the drive as a duplicate (same drive listed twice).   Getting message file not found in develop module.   How can I relaunch my old catalog? would that fix this?

Im having the same issue updated to Catalina 10.15 then upon opening Lightroom got message about catalog being incompatible and have to choose a different catalog.  All my files I work with are on an external drive, I noticed that the drive is now handling file paths different than before.  "volumes" is missing before the drive location.  It is also showing the drive as a duplicate (same drive listed twice).   Getting message file not found in develop module.   How can I relaunch my old catalog? would that fix this?

Having the same problem here as Christopher. Trying to role back Lightroom Classic to Version 8...

Checked and all the files are online and in the original locations.

@3302407: When you click 'Choose a different catalog' in the error dialog, you can click to create a new one in the next dialog.

@7198024: Apparently Lightroom needs to read info from the images (depth info), so one thing to check when you get this error is if the originals are online. If they are not, this may cause the problem.

Following the upgrade to Lightroom Classic v9 (Windows 10) several catalogs upgraded successfully. But the next had the same error message as above
‘Lightroom encountered problems when trying to update the format of the catalog file and cannot use this catalog in this version of Lightroom’
I tried to upgrade the most recent backup but encountered the same error message. I am stuck - is there a solution?

I have the same problem with my new catalog. None of the recently added pictures are available and I get a message that I cannot access files.  How do I get out of Catalina upgrade or do what Joe Kelly did.  I do not know what he means by 'create a brand new catalog. Where and how would I do that?

I love problems that fix themselves! Much easier to deal with.