First time I have flown this one after many flights with the -800, the autopilot won't work? Any clues please guys? generators are normal and everything setup for normal flight as in the -800.

Do you have realistic AP engagement enabled?

Maybe you have given manual control inpud. If you have selected the option "realistic autopilot engagement" in the FMC you can't engage it when the control culom is not centered.

Thanks a lot guys, I didn't realise this was to be done. It wasn't in the -800

Any time you switch variants (or even liveries) it's a good idea to look through your options (at least the first time using it) to make sure everything is as you prefer.

Thank you again for the super quick response. It shows how many people that know this aircraft inside-out.