Business .Manager File Won't Open on Either Mac or Windows Computers

@eko He said that he tried to open it from the cloud.
While you are thinking the cloud version of manager.

I think he means he keeps some files on the cloud for his team,
to open on the desktop or server versions of manager.

@NEC Here is somethings I found that may apply to you.

I also suggest that you make 3 copies of your business file from now on.
And store one on your computer, one on a jump drive & and the last on a external hard drive.