Hello Miltonfromqld,
Thank you for reaching out to Apple Support Communities, and we'll be happy to help in any way we can. We understand you're having issues with notifications for Gmail. To clarify, are the notifications not showing for this email account only in both the native Mail app and the Gmail app, or just the Gmail app?
To start, check out the details here about notifications: Use notifications on your iPhone, iPad, and iPod touch
If you need to change the notification settings, follow the steps listed here: Change notification settings on iPhone
If this only happens with the Gmail app, try these steps as well: If an app on your iPhone or iPad stops responding, closes unexpectedly, or won’t open
"If you found the app on the App Store, contact the app developer."
If it also occurs in the native Mail app, try removing the account and adding it again: Add an email account to your iPhone, iPad, or iPod touch
We hope this helps.
Cheers!