Signing with digital signature does not work in Adobe Acrobat Pro DC

I am using a MAC with Yosemite:

Here is my version of Adobe Acrobat Pro DC

I have made an interactive pdf but the digital signature area is not able to be signed. I could create the box though.

The other areas are fillable:

When I click on the signature box--to sign the form with a digital signature (which I do have, created already), I get a transparent gray-ish box and am not able to sign.

If I hit the esc button it will go away.

I need this to work, so please fix!