We were using TenFourFox browser on an older iMac G5. Later, I checked its security settings and found that it thought the AOL site was not secure, probably from the Heartbleed bug. Once I turned that off, we we were able to connect to and use AOL.
AOL should by now be safe from the Heartbleed bug. However, I
can't say much about this without knowing the error or warning
message you got, or where exactly you turned off (?) TFF's security
settings regarding AOL. Overriding security warnings is generally
not a good idea. If AOL was affected by Heartbleed, it'd be wise to
change your AOL login password, assuming you now have a secure
The AOL homepage loads fine for me. Regrettably I cannot test any further than that because I don't have an AOL mail account. Without knowing the contents of the error message I don't know what else to do.
Maybe try setting the user agent string to Firefox 52? (TenFourFox Menu>Preferences>TenFourFox>User Agent)
This doesn't look like a problem with TenFourFox, it looks like a problem on the AOL website. Please try again at a later time or just go to www.aol.com, then click on the letter icon to get to your email account.