Grasshopper doesn't install

Hello,
I’m using a 5.1.2 rhino version, and downloaded grasshopper from the site, but the installation won’t open and showing this error:

what can i do?

thanks

You will need to update to the latest Rhino5 Service Release. SR13 or 14 I think by now. It’s free! And you get loads of bug-fixes thrown in too.

5.1.2 seems to indicate this is on mac.

I think you have to use the WIP version of Rhino 5 for mac.