You cannot sync catalogs on two machines.
If you want to access the same Lightroom Catalog on both machines, you should store your Catalog and original images on an external drive so that you can plugin the external drive on the machine on which you want to edit images.
Refer this tutorial to transfer catalog to external drive :
Thank you but it didn't help me.. I actually put my pictures from the Mac photo app,on my desktop. And then I made a file on my hard drive, and then put those pictures into the file. Now when I upload light room, I just click on the file that is under my name instead of in the pictures.
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Thanks for the update.
Is your issue resolved?
Have you got all the images in Lightroom now?
The steps that I shared were to transfer the catalog from your PC to new machine.