Why you don't see signatures from the web version of Dropbox Sign on the mobile app and vice versa?

The Dropbox mobile app and the Dropbox Sign website are two separate entities and don't currently sync together. Because of this, you won't see your saved signatures from your website account on your mobile app account, nor can you save signatures on the mobile app.

You can still access documents sent from the Dropbox Sign mobile app on dropbox.com and the Dropbox mobile app.