The most common reason this happens is because your email client auto-corrected the "To" field in your email to our support email address.
Please try again and be sure that you entered email@example.com (not firstname.lastname@example.org) in the "To" field and that you've properly typed the unique subject code shown to you on the "Edit signature" screen in your HelloSign account.
If your mobile signature still doesn't appear, please click the "Contact" button at the bottom of the HelloSign page, or the "Help" button if you're logged in to your HelloSign account, and send us a message about what happened step by step.
If an error occurred, please include the error code if one is listed. Don't forget the select "A Technical Issue" as the "Reason for Ticket" and enter the email address you use to login to your HelloSign account, and our Support Team will investigate!