Siemens Condenser Tumble Dryer WT46S598GB?

Just bought this condenser dryer as unused but it came without packaging and it's obviously been stored in very a dusty environment. When 1st trying to use the machine the programme kicked in but the drum will not spin & after approx 10 secs the 'clean filter' alert flashes.
Initially I thoroughly cleaned the filter and when this failed to resolve the problem I soaked the filter and ran clean water through it hoping that this would clear the problem. However I'm still getting the same error message suggesting that the filter isn't functioning.
Is there a sensor within the machine which may also be covered in dust which would cause the same message to be shown & prevent the unit from starting? Or any other suggestions would be greatly appreciated. Many Thanks.