2010 Holden Colorado help please

[Dude]

Hi Team, we have a 2010 3.0 diesel 4WD crew cab manual and are having issues with the 4wd not disengaging. Yesterday it didnt come out of 4wd at all for several kms, tried everything from stopping, reversing, shutting the truck down etc... After another few kms, stopped and out she came, but the "check 4wd" light is now on the dash and she won't re-engage at all now? i am guessing it might be a solenoid fault or computer error of sorts??? Can anyone make any simple suggestions as to what might be the cause or can you suggest somewhere in Chch that can look at this for us. (Blackwells Holden are a pack of wan@#s and i never want to ever deal with them again (Factory Warranty ran out 2 weeks ago to the day) so a good 4wd specialist in or near Hornby would be great? TIA

[Sonic]

1. Ignition off, hold all 3 2h, 4l, 4h buttons together.
2. Turn ignition to "reds"
3. Hold for 30seconds