As an additional confusion...I removed the pbank0 line, and expected the part to rotate..... but it didn't

I was expecting to see the thing spinning round ( to confirm it worked ) and then add in the $pbank0 command to link it to the guns. The code I posted was my start point. I should have seen the thing revolving constantly in the same way as the 'habitat' section was.
Only once I had that working was I going to add the extra line. I would then know it was working, and could tell if the pbank0 line was having an effect. Never got that far!
If it won't turn full stop, the linking to the gun bank was pointless...and would only have got me even more confused!
What could be causing the part to not rotate?