Before requesting a DPF regen clear all fault codes.
For the request to be carried out all conditions must be met including at least 10 litres of fuel, temperature before cat of 240°C, coolant temperature of at least 75°C.
The optimum regeneration is achieved after 20 minutes at a constant speed of at least 60kph.
Also this website will give you some more information about the fault codes:
http://bmwfault.codes