esignature field disappears

After creating a PDF I added a digital signature field so the PDF can be signed but when I email the PDF to the person who needs to sign it the signature field disappears so they are not able to sign the PDF.  With this I also noticed the PDF icon looks different in that it show a red belt on it; not sure if this matters.  Also, the person signing is running the latest version of Adobe Acrobat Reader DC and the program being used to create the signature field is Adobe Acrobat Pro DC.

How do I fix this so the person can sign the PDF?