[GNC] Gnucash won't open

[Alison Fox]

Hi.
Hoping someone can help me.  I am on a MacAir running MacOS High Sierra version 10.13.4
When I went to open Gnucash, it will not open.  I tried several ways, but it says the software may not be compatible.  I downloaded the latest version.  It downloads and I saved and open the application.  It verifies it and then asks if I want to open it even thought from Internet.  I say yes.  It looks like the icon is bouncing and about to open, but then it simply vanishes.
I can't get my files and I can't open the older version or the one I just downloaded.  Any suggestions?
Thanks.