I have downloaded the Belgium AIP on my pc and tablet (--> all plates are Downloaded)
Now i just see 8 aerodromes. EBAW, EBBR, EBCI, EBGB, EBKT, EBLG, ELLX and ABOS.
Not the other aerodromes, e.g. Spa, EBSP.
When i click on the Spa aerodrome on my pc, it says: There are no plates available for this specified airfield.

The Belgium AIP is free, so why can't i see the other plates?

There is no VAC published for EBSP by Belgium in their international AIP distribution. If you have a contact within Belgian AIP perhaps you could ask them the reason for this, as if they wanted to, they could publish it and then we'd be able to include it for you.

I have no answer from Belgocontrol / AIP production yet.

I see the EBGB / Grimbergen VAC in Skydemon, but is has no blue map-marker (will not overlay the plate onto the map itself).
When i look at the Belgium AIP in Skydemon:  
Aerodrome / AD2 PVT Private Aerodromes: 
I see the approach charts from EBGB Grimbergen en EBSP Spa