The reason is the capacitor C1 on the electronic board which lost capacity. You find the electronic board in the upper region under a white lid. The capacitor is the big yellow part besides two black relais. It's capacity is 1 uF and it is made for 275 VAC. If you exchange the capacitor the dehumidifier will probably work.
!!! CAUTION !!! The electronic circuit is not isolated from the line voltage (230 VAC). Remove the power plug before opening the dehumidifier. Be careful of the voltage which the capacitors of the board have even after switching it off.
The operating voltage of the electronics ist generated by a voltage devider. The capacitor is part of this devider. In my case the capacitor had a capacity of only 0.3 uF instead of 1.0 uF. That is the operationg voltage for the relais breakes down from more than 20 V to 10 V. If blower and compressor are switched off the voltage is 20 V. During the switch-on procedure first the blower relay is activated. The voltage goes down to 15 V, and the second relay for the compressor will never switch on.
This was the answer from another Dem 10 link from Robernd - I gave it a go a couple of weeks ago and it works like new! Bought a capacitor and solder iron off ebay!