Affected version(s): 7.10.6
E-Mail Signatures that are created within App Suite are not visible and useable using App Suite on Mobile Devices.
This was a design decision within App Suite 7.10.6. Signatures are separated into Desktop Signatures and Mobile Device (text-only) Signatures in order to prevent a cluttered UI experience on Mobile devices.
Create a separate text-only Signature within the App Suite UI on a Mobile device.