On the file stored on the computer, the most likely cause is that the AOL program got disconnected from the file. This could happen if you moved folders around, renamed some files, or if a power failure interrupted writing the file.

There are then two tasks:

1. Reconnecting the file with AOL. This is usually a setting. AOL's local program needs to know the path to the file and the filename.

CAUTION: If you have been using it since then, the new emails will be lost if you reconnect the old mail file, unless you export them first.

2. If the file is damaged, it must somehow be repaired. I don't know if the software can do this or not.

It might be easier to extract the text of the old emails from the file by opening the file with a text editor and separating the emails (I have done this before). Just edit out the codes between the text. You might have to rename the file as a .txt extension to do this.