iCloud Mail Error Message

I recently bought an iPhone 8, and signed up for an iCloud email. In the mail app, I keep getting an error message on the bottom of my screen reading “Account Error: iCloud”. Below that is some blue text reading “Details”, which seems to be a hyperlink (but the link does not do anything). I tried to send an email from my iCloud in the mail app, but a message popped up reading “Cannot Send Mail” and “The username or password for “iCloud” is incorrect.” I’ve tried logging out and signing back in of my iCloud account, but I still experience the same issues. What can be done about this? Pictures of the problem are attached below