Hotpoint Aquarius DWF30 dishwasher

[kizzicat]

My dishwasher cleans everything on the lower shelf with no problem. However the contents on the upper shelf remain, on the whole dirty, and little evidence of having come into contact with water.
I have discovered that the upper arm is not rotating but have no idea why. I can rotate it freely by hand when not in use.
Any ideas would be greatly appreciated - Thank you.

 

[Diyisfun]

Take it off & clean it, I bet all the holes are blocked up.
Its a pain in the A***se

 

[kizzicat]

Thanks for the suggestion but that was the first thing I tried! Sorry.
Have also checked that water outlet lines up with rotator arm.
I know there is not a problem with the water supply or water pressure because the lower arm is working fine.
It's quicker to wash by hand!