Missing iCloud Mail

I mistakenly deleted my Apple (iCloud) Mail app on my iPhone 8 Plus and upon reinstalling the app, it asks me to sign in to iCloud Mail, Gmail, etc.. When I attempt to sign in to iCloud Mail, I get a message telling me “this account has already been added to your iPhone”, with no option to go further.

I was advised to reset my home screen in Settings, to restore “factory settings”, but this accomplished nothing more than erasing a couple years of organizing on my phone. How can I re-connect to the iCloud Mail account and email files? At this point, I cannot retrieve or access iCloud Mail unless I use my iPad.

Thank you for any help you can offer.