Issue with two separate Catalogs

To use the same catalog on two computers, you need to have the catalog, as well as the images on an external drive that you move between the computers.

This will probably make LrC slower, how much will depend on the type and interface of the drive. I imagine that using a 5400 rpm spinning drive will be quite slow.

You would need to copy both catalog folders to the external drive, open one of the catalogs, and merge it with the other catalog. (File > Import from another catalog)

It is likely that LrC will report most, if not all of your images as missing, so you have fix that in both catalogs before merging them.

See https://www.lightroomqueen.com/moving-lightroom-free-ebook/

https://www.lightroomqueen.com/how-to-lightroom-catalog-multiple-computers/

https://www.lightroomqueen.com/lightroom-photos-missing-fix/

Another method (that others probably will warn you against) is to keep the catalog and the images on Dropbox.

I have done this without issues for years, but there are certain rules that need to be followed strictly.

• In Dropbox > Preferences > Sync, Save hard drive space automatically must be set to Off.
  If set to On, local copies will be deleted, and LrC cannot work with images in the cloud.
• In Dropbox > Preferences > Sync, New files default must be set to Available offline.
• If both computers are running, only one of them can have LrC open.
• Dropbox must have finished syncing before a computer can be turned off.
• Dropbox must have finished syncing before Lightroom can be launched.
• Breaking the last two rules may lead to catalog corruption.
• Using any other cloud storage than Dropbox (like OneDrive) will most likely lead to issues.

Also as an aside, i believe i've lost some holiday images from July 2022 from my laptop? Is there a way to revert back to previous save points but without losing images since? 

By @SCOTT5CDD

Does LrC report the images as missing? (exclamation mark in the top right corner of the thumbnail)