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The best option is by using official AOL email app. This application is designed to work best with AOL. Open Play Store. Search and download Alto - Email Organized for You
After installing Alto, open it. Then sign in or add your account. That should work. This is the app --> https://play.google.com/store/apps/details?id=com.aol.mobile.altomail&hl=en
Please let me know if that didn't work, so we can continue troubleshooting.
There is also another official app named AOL Mail, News & Video. You can install and setup your AOL account on it as well --> https://play.google.com/store/apps/details?id=com.aol.mobile.aolapp&hl=en
These official apps are designed mainly for AOL. Refer this article --> https://help.aol.com/articles/aol-mail-mobile-mail