Hi Welcome to JustAnswer
Give me a moment. I will get back to you with my findings.
Which email service provider you are using ? like google,Yahoo etc
Try these steps one by one and see if it fixes your problem :-
Ensure that the Address Book category menu is set to All Contacts
The Address Book can be sorted by category. The listings on your Address Book may be hidden depending on the category currently selected. To change your category listing, please follow the instructions below:
Verify whether your Address Book is present in AOL WebMail
Sometimes, the AOL Desktop Software can have problems retrieving your Address Book. Verify whether your Address Book is accessible on AOL WebMail.
Reset your Address State
Resetting the Address State will help re-synchronize the Address Book. To do so, please follow the instructions below:
Run Addressbook Sync Fix
Addressbook Sync Fix is an automated utility that helps you resolve issues such as missing or blank Address Book. Once you run this utility, sync issues with Address Book and Favorite Places will be resolved.
IMPORTANT: This solution does not work for AOL Desktop 9.7.
Delete Address Book files
Some Address Book files of the screen name may have been damaged. Deleting your Address Book files may help resolve the issue. Once these files are deleted, the AOL Desktop Software automatically creates new ones. Please know that deleting the Address Book files will not delete the addresses in your Address Book; only the files linking the Address Book on your computer to the Address Book stored on AOL servers are deleted.
Activate tunneling using AOL Keyword: Browser Fix
You may face this issue if tunneling is not activated on your AOL Desktop Software. Tunneling allows your AOL Desktop Software to work better with your local internet service provider (ISP) network. To learn how to activate tunneling, refer to our help article Activate tunneling using AOL Keyword: Browser Fix.
Note: This keyword can be accessed only within the AOL Desktop Software.
Upgrade the AOL Desktop Software
Upgrading to the latest version of the AOL Desktop Software may fix this issue. Check whether your computer meets the minimum system requirements for the version of the AOL Desktop Software you plan to install.
You can get the latest version of the AOL Desktop Software from multiple sources. Check out the help article Obtain the AOL Desktop Software for additional details.
Uninstall and reinstall the AOL Desktop Software
If the issue persists, we recommend that you uninstall and reinstall the AOL Desktop Software. Uninstalling the AOL Desktop Software removes all damaged and non-repairable files, and reinstalling the software installs new, error-free files.
Please click the link corresponding to the version of Windows on your computer for instructions to uninstall the AOL Desktop Software.
Copy Address Book index files from old folder to new folder
If you're still missing your Address Book, please follow the instructions below:
Did you try contacting AOL ?
Do you have backup of it somewhere ? Almost same contacts in some other email id ? If so we can import that contact list to your AOL account.