Trouble resetting Yamaha DX21

"[email protected] [YamahaDX]" <[email protected]> 16 Sep 2019 22:54:15 +0000

Newsgroups	gmane.music.equipment.yamaha-dx
Message-ID	<[email protected]>

I received a TRS80 cassette cable today and I can’t reset the factory settings. I don’t know what I did wrong. I changed the battery, connected the MIDI in and out, and connected the cassette cable to my amplifier. I keep getting ERR. CASS.