"Open With..." App list in Default Email Client vs. Gmail App?

[Android Central Question]

We use the app called SignNow to review and sign warrants. With the latest SignNow update, SignNow no longer appears in the "Open With..." list when we try to open a word document (.docx) from the default email client on a Galaxy Note 10.1. Android OS Version 5.1.1.

What is weird is that if we use the gmail app and configure it to the same exact email address, and open up the word document in the same email message, SignNow magically appears in the "Open With..." via the gmail app,

Why would the android default email app not bring up an application that seems to show up thru other apps? Is there a way to get SignNow to show up in the open with... list through the default email client?

I've tried removing/adding email accounts, and a factory restore this morning; neither option has produced results yet.

 

[Rukbat]

It could be GMail or it could be SignNow, but it's probably easier to get an answer from SignNow. Their email address is support@signnow.com, so trey emailing them. Asking Samsung (anything) is a last ditch effort - I'd rather ask a blade of grass. And asking Google will get you different answers, depending on where you ask them.