Getting white empty box when I try to request a document to be signed out of Microsoft outlook

When I click my "add on " button on the top ribbon of outlook " Send for Signature" it will let me go thru the standard steps of adding the file and email reciepient but whne I hit " Contiunue" with the box check Preview and send it brings up a white screen verses the document to proof and sen d for signature.  Please help.