I'm unable to open a project saved using a Mac (Sierra 10.12.4 running Avid MC 8.5.3) on a Wndows 10 machine running the same MC version. I transferred the project folder usiing two different mechanisms, via Google drive and a Compact Flash card, with the same result. Any ideas?

In case it matters, the project started on Windows MC 6.5.4 installation before being moved to the Mac.

You may create a new project on the Windows machine with the very same name, size, and frame rate of the Mac project, and just copy the bins over there, they should open. Weird anyway, projects should come across.

luca.mg is spot-on.

Keep in mind, Avid is different from other software.  Avid's editing data is stored in the bin files.  The ".avp" PROJECT file actually has almost no relevant project data in it.  The bins are far more important.

Just to be clear - you WERE able to open the 6.5.4 project on the Mac and continue working on it, right?

That's sort of what I did. I opened up the original MC 6.5.4 project in Wnidows MC 8.5.3 and overlaid the bins that have changed from Mac MC 8.5.3.

usatraveler:

Just to be clear - you WERE able to open the 6.5.4 project on the Mac and continue working on it, right?

Yes.