For troubleshooting the network issue, you may turn off your iPhone. Then you can start it again. After this, you can connect to the network. See whether your AOL mails are accessible now. When the problem has still not been resolved, you can connect with your internet service provider and convey the network problems.
Also, see the other fixes to try: https://www.errorsdoc.com/email-support/why-is-aol-mail-down/