IOS 13 Email Problem

Updated iPhone X to IOS 13. Go to mail app and choose an email from list of emails, which chosen email, like before, then appears in full in a new window. It is now impossible to switch to next email from that page. The up and down arrows at top right of screen do not work. Moreover, if I trash an email the next email does not appear but instead I get a message "No Message selected," and thus always have to go back to original email list to get the next message. This never happened before the update.