I have recently had increasing problems with the gears not changing, not starting, stalling at lights etc, with the transmission warning light on.
The only info I could find was a suggestion that the gear change actuators may be seizing, so I removed & stripped these. There was nothing wrong with them, but on refitting them the fault had worsened to the point that the car would not turn over just the warning light on all the time.
The fault was a broken data link wire inside the conduit going down the front of the gearbox at the point where it separates to the two actuators and the ECU/clutch pack.
A cheap and easy fix once I found it, certainly worth looking for if you have gear problems on these cars.
I hope this will be of help to others.
Cheers

I recently experienced similar problems which did turn out to be a seized actuator. This was resolved and car has run really well for around 4-5 weeks since. However last night car would not start and seems to be showing same symptoms as you ha. Cannot get N indicated, and the power train warning light is on.
How did you isolate the data link issue?

Sorry I've taken so long to reply, finding the fault was more luck then anything else. I just noticed the broken wire inside the conduit at the join where the wires from the actuators meet the main harness low down in front of the g/box. The conduit on mine is open at the joins which is an obvious weak point. I had been trying to find a decent (understandable) wiring diagram without success. But I have some experience of data links from HGV work & they are a source of problems. Data links are fairly obvious as they are always twisted pairs of wires to reduce interference. Be careful when testing as they run on variable low voltage signals, if you put full voltage down them it can damage ECU's. I would recommend stripping off the conduit & inspect visually, you could also pull the wires to see if they spring which means the wire is broken inside the insulation.
Sorry again that I can't be more helpful than this.
Hope you find your fault.

Many thanks for this Big Bob,

I'll let you know what I find. Probably will not get to it until middle of next week but its a clue any way.