downloading email

Occasionally I have difficulty downloading email only on my iPhone 12. Never with my desktop. Most frequently with AOL, but has happened with iCloud. My hope is someone understands and can explain what is happening. While it seems the issue be with the AOL server, turning off the phone and waiting and retrying apparently changes something with the phone. My description.....

There is a notification I have mail, red circle on the mail app. I open Apple Mail and it lists the mail account has one and I select and it goes to the inbox, which is blank. I get the downloading mail symbol and after awhile, (20 seconds or more) it stops and at the screen bottom I get the message "Updated at .... -1 unread, Account error AOL Details ..." and the details says connection to the server failed. See photo below...

If I wait long enough like overnight (phone left on), it will download and I see in the morning, or I can trick it by turning off the iPhone for five minutes or so and then it will download. Sending email has not had delays.