You're welcome for the reply, Wbjimmy.
It sounds like you may have already isolated this and done most of the troubleshooting yourself. Which is awesome, but we wanted to make sure of a few things before moving forward.
You mentioned reinstalling the Mail app. Did you delete the app and reinstall it from the App Store or did you uncheck iCloud Mail in Settings > [Your Name] > iCloud > Mail? We were a bit confused about how it was mentioned.
Both of these steps might be good to test out, if you haven't already:
Re-enable iCloud Mail
- Go to Settings > [Your Name] > iCloud > Mail and uncheck it.
- Restart your iPad - Apple Support
- Go to Settings > [Your Name] > iCloud > Mail and check to enable it again.
- Test out the issue.
Delete the app and reinstall
- Delete apps on your iPhone, iPad, and iPod touch - Apple Support
- Download the Mail app again from the App Store app.
- Set up your email once more: Add an email account to your iPhone, iPad, or iPod touch - Apple Support
How to delete an app
1. Touch and hold the app.
2. Tap Remove App
.

3. Tap Delete App, then tap Delete to confirm.
Keep in mind that some built-in Apple apps can't be deleted from your device, so you might not see the option to delete an app. Here’s a list of built-in Apple apps you can delete from your device. If you can't delete an app that's not made by Apple, disable parental controls, then try deleting the app again.
If you touch and hold an app from the Home Screen and the apps start to jiggle:
1. Tap the Remove icon
in the upper-left corner of the app.

2. Tap Delete App, then tap Delete to confirm.
3. Tap Done.
Learn more
- With iOS 14, instead of deleting apps, you can remove apps from your Home Screen, so that they appear only in your App Library. Learn more about using the App Library.
- If you delete an app, it doesn’t cancel in-app subscriptions that you might have. While deleting an app, you might see a Cancel Subscriptions option. Learn how to cancel your subscriptions.
If that doesn't solve it, then it would be best to connect with Apple Support
We hope one of these do the trick, but if not Apple Support will take it from here.
Wishing you well, cheers.