With delisted coins, they no longer maintain the wallets - so they probably haven't synced it since 2015.
I doubt they're going to go through the hassle of reviving the wallet just for you either.
Especially on AEON, which kinda eats resources like Monero did years ago. They at some day headed for implementing pruning on their chain. The DB backend, did that ever draw on par with XMR codebase?! Not to my current knowledge.
Exchanges utilizing light wallets aren't all to common, either. After delisting could be a considerable option.
Bittrex features an overview page regarding their wallet connectivity,
https://bittrex.com/Status Nothing similar available for most of the other sites.