90% of my DVR recordings are gone

Cox switched to a different Cloud TV system and migrated all recent recording over to hardware on Comcast's network. All recording made before August 11 were deleted. You should have gotten a email and/or a notice on your bill. See here. There have also been reports of issues of some recordings made after that date having some issues too. I think it's a known issue being worked on but feel free to contact Cox to confirm.