Digital signature fields not showing on tablet

I have created a fillable form on adobe acrobat pro dc and I added digital signature fields. I have guys that are in the field working and only have access to a form on a nexus tablet. When they install adobe reader and download the form that I sent to them everything shows up except for the digital signature fields (the most important part). I am not sure why only the signature fields do not show up, but if they are on a laptop the fields show up and everything is fine. It would be nice that for them to be able to sign the forms and email them back to me so I can have them on file.