In some situations, your email signatures may not be applied due to different reasons. The most common solution to the problem would be the Re-Sync feature, which re-deploys email signatures to all users (Global Signature) or only to the selected ones (User-Specific Signature).
Follow the steps below:
Step 1. Access the BulkSignature app.
Step 2. Go to Signature Management.
Step 3. Locate your email signature.
Step 4. Click the Re-Sync button.
And that is it! The process will relaunch your email signatures. Make sure reload your Gmail after that.