Ok this is a wild one. So I have a 2015 macbook pro and a custom built pc. I keep my photos and catalog on an external drive, even with importing I have lighroom import the photos to the drive and convert them to dng files. Recently the pc got a new drive and was basicfally another computer. I got lightroom classic installed onto the pc and then opened it up with the catalog from the external drive. For some reason it popped up with all the photos but said that it could not locate files and that they were missing. 2 years of files missing. But I had literally been using it on my macbook 5 minutes prior. So I located the folder with all the files and it is all good. I then need to go back to the macbook to do some work back on the go and then the macbook said that files were missing so I located them. Everything all normal again and then went back to the pc and long and behold files missing. It has been going back and forth like this for a while. From what it seem that when going to the other device it reads the drive as a different one does any one by any chance have a solution or know why it did this in the first place. Adobe told to just move the catalog to the comptuer and when needing to switch just copy and paste which is reduntent I do not have time to keep moving my catalog around. I was able to work just fine before having to replace the drive it never did anything like this until now.
I know this is super wierd I have to go back and forth devices almost daily with my work and I hate using the internet to do syncing or anything.
This is actually as expected. Windows uses drive letters and MacOS uses disk names, so the path to the same image on the same disk is different, depending on which OS you use. On Windows it is something like D:\Folder\Image and on Mac that would be ExternalDiskName/Folder/Image.
There is a method that should work, because Lightroom then uses 'relative' paths that do not include the disk name. Move all the images to a folder hierarchy inside the catalog folder on the external disk. Now the path becomes something like .../Folder/Image on both systems.