Are you not able to access your AOL Mail on iPhone? If yes then you need to implement the troubleshooting steps so that you can make your AOL Mail to start working fine:
 In the first step, you need to check whether you have an active and working internet connection on your iPhone. If not, then turn on and off the Airplane mode and then connect to your WIFI network.
 Check the Wi-Fi network setting entered in your iPhone are correct. If they are wrong, then reset it.
 You can also try removing your AOL account and then adding it back on the iPhone.
Lastly, you can contact experts via aol email tech support number to seek their help. The professionals will make sure that they resolve the error faced by you.

For more info click here: aol email customer care | aol email support phone number