Hello Lamom78,
The first thing we would suggest would be to power cycle the iPhone using these instructions: Restart your iPad - Apple Support While simple, this can refresh the iPadOS, apps and connections.
If you continue to have an issue, we would follow these steps found at If iCloud Mail isn't working - Apple Support:
1. Check the system status of iCloud Mail.
2. Check that you turned on iCloud Mail:
•On your Mac, open the Mail app then choose Mail >Preferences. Click Accounts, then select your iCloud account in the sidebar. Under Account Information, make sure that the account is turned on and the status is online.
•On your iPhone, iPad, or iPod touch, go to Settings > [your name] > iCloud and check that Mail is turned on.
3. Make sure you that haven't exceeded your iCloud storage limit. If you exceed your iCloud storage limit, learn how to make more space available in iCloud.
4. Make sure that you're using the latest version of software on your device.
Be sure to check that page for additional information.
Have a good day.