Why isn't my Sony CCD-TRV98 not reading 8mm?

This Hi8 handy cam is suppose to be backwards compatible but its not reading 8mm tapes. I know for a fact that they have video on them. When I play the 8mm I get full screen video and audio static. Also on playback the camera sporadically switches from LP and SP. I've tested it with a Hi8 tape and it plays just fine. The tapes have not been in damaging conditions or near a super magnet. Is there a setting that allows 8mm? HELP!