No drive from Steptronic

Hi All, So my steppy has lost all drive. It happened just a mile from my home down a gentle country lane. It just coasted to a halt, the engines running fine just no reverse or forward gears. I've got her towed home and checked the gearbox fluid which was low, and topped it it up. Still no drive though. I was going to change the fluid completely and filter as my next effort to solve the problem, however I've realised the wheels still turn when the car is in park. I don't know a great deal about these boxes, but it would suggest the problem isn't fluid as I assume the park facility is a mechanical lock.
The selector arm seem to be travelling the full distance so I don't think it's cable adjustment. Has anybody any experience of this fault?
I'm hoping maybe a nut has dropped off or something just as the selector enters the casing - I think I can remove the sump, filter and valve block and maybe see what's going on? I've never worked on an autobox let alone a CVT so not too confident with what I'm doing. I'm thinking of maybe just getting another box and swapping it out. Any advice would be appreciated.

I don't know much about the steppy but I thought park "locked" the box on an auto.

Were both wheels off the ground when you turned the wheels?

On any "normal" auto box, If the car is jacked up at rear, then even in park the wheels will rotate, due to the action of the differential.

However one wheel will turn one direction, and the other will react in the opposite direction.

Wheels on the ground then the gearbox will "lock up" and car will not roll in either direction.

I presume a "steppy" will act in the same way.

Yes, both were off the ground. I didn't realise the diff allows the wheels to rotate though. It looks like I'd just better change the oil and drop her back on the ground before I write the gear box off

IT may be the filter in the box that needs changing and of course the oil. I say this only because on wheeler dealers that had the same and cured it by changing the filter/oil

The box is knackered. Replacement on its way - getting ready for my first ever sub frame drop