GMail app not displaying signature Issue:

When replying or creating a new email, the signature does not load.

How to replicate:

From the GMail app:
Settings - mail@mail.com - Signature - set any text - create a new message


Notes: there's no Google Account set on this phone. The GMail and Google Play Services APKs were downloaded from APKMirror

What has been tried:


Setting up Exchange and YahooMail accounts
Clearing the app's data and reinstalling it
Restarting the phone
Changing the phone's language from Brazilian Portuguese to English (United States)


What else can I try?

Thanks in advance

GMail versions tested:

7.5.21.158049789.release
7.5.7.156101332.release


Google Play Services versions tested:

10.2.91 (430-144333517)
11.0.55 (430-156917137)


Device:

Moto G4 Play (harpia)


Android version installed:

6.0.1 (stock, non-rooted)
Based on the suggestions given by Gmail Help (website) forum  just double these issues:


Make sure you are not using an alias email to send your emails
Usually the signature does not show when drafting a message but is appended when sending (try tapping 3 dots at th bottom of message and check
if see the signature)
Sometimes its the way the app is designed:



  The signature does not show during drafting a message it is appended
  upon sending.
  
  Try checking  in your "Sent Mail" and if you don't see the signature,
  there are three faint dots at the bottom of the message, click that
  and you will see the signature.


Sources:


Why is my inbox signature not showing in my email after I send
Signature hidden by "three dots"
Adding a signature to reply and forward emails