I recently logged on and all my emails were gone. how do I get them back and can cox restore them.

The rep is supposed to open a ticket and escalate your problem to the third-party contractor administering their email service.

There may be a couple servers providing your email service.  The server you're logging into is the web front-end with your profile and perhaps another server...a file server...contains you personal files (email and attachments) and is perhaps undergoing maintenance.