I am trying to work on an after effects Project that a collaborator started on windows, while I am on a mac. I get this error: "After Effects error: The file you are attempting to open was created with After Effects version 12.2.1 (windows 64) and cannot be opened with this version." Is there anything I can do to get this to work?
The version of AE on your Mac must be the same or newer than the version used the save the project on the Windows machine. You will get a slightly different warning but the project will open.
The only other option is to open the project on a machine that has the same version and do a save as a previous version. You keep doing this until you get to the same version you have on the Mac. AE has never been backwards compatible. If your Mac's version of AE does not support the same features that are supported in 12.2.1 (by the way I don't think that is the latest build of 12) then you'll have to upgrade the software on the Mac.