If I put a normal cassette tape in the slot, the monitor recognises that there is a tape in there, but there is no audio playback. Anyone had this problem / found a solution.

Not that I use cassette tapes a lot, more likely to use an adapter for mp3 player or phone. .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

did you not use this output for your car pc.. V8 facelift Range Rover Autobiography 22" wheels.
1976 Harley Davidson Iron Head Sportster

Cassette player problem ? Oh No.......... I am sure I can find a 12v 8 track player you can mount under the dash with some self tappers.........

Seriously, I often think I'll try a tape in my car, but I've a feeling its either not gonna work, or unravel itself all over the insides and stuff the lot.

Perhaps the drive belts have perished and the tape doesn't go round anymore......... 2011 Range Rover Vogue SE 4.4 TDV8

Previous cars :
2003 Range Rover Vogue TD6
1999 Discovery Td5 ES
1995 BMW M5 3.8 6 speed
1992 Range Rover 3.9 Efi Vogue
1992 BMW M5 3.8
1988 BMW 735i SE
1989 Ford Sierra XR4x4 2.9i
1981 Ford Fiesta Supersport

@ daveo

Have it wired both ways

May do some tinkering in the boot, if it ever dries up a bit  .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

Mine stopped playing in about 1990!

 2005 L322 Vogue Gold gone
2006 L322 Vogue Black gone
2011 L322 Vogue Silver gone
2011 L322 Autobiography Black gone
2015 L405 Autobiography LWB Black gone
2019 L405 P400e Range Rover Autobiography LWB Eiger grey / black roof gone
2001 P38a 30th Anniversary Wimbledon Green gone
2019 L405 P525 Autobiography LWB British Racing Green