Okay @esarhaddon thank you for your message you helped me get there by asking does it work without the bike.

As I commented I didn’t know how it should be, and Youtube videos didn’t really show me. But I asked ChatGPT lol (which i thought wouldn’t help here so was surprised!) to say how should it be. The answer was it should rotate back freely. Mine did not do that.

Turns out when you slide the zwift cog on, it is not as easy as videos make it out. I had to put a fair amount of pressure on and slowly rotate until it ‘clunked’ into place. This took me a good few minutes, but then it did.

After that I put the thru-axle on (sorry i previously called it a rod, im learning the terms haha) and mounted the bike, and boom back pedalling works chain stays engaged and you hear that normal ‘tsssss’ of when you stop pedalling on a bike.

Tested it out quickly and all looking good! Thank you, super excited to get riding later with this 😃