SOLVED: I was stupid. One litre less water in the kettle meant my temperature probe wasn't touching the water and strike temperature ended up being higher than intended, which obviously obliterated the enzymes and no sugar was produced.
First total failure of my homebrew journey, and I have no idea why... I was really looking forward to this brew, a pitch-black stout with smoked wheat, chocolate malt and black malt. For yeast, I was anticipating to try Alzymologist's speciality.
However, it's been four days in the fermenter and I've pitched three yeasts – first the Alzymologist (made a starter), then my usual fresh yeast without a starter and for the last desperate attempt some dry wine yeast – I can only come to the conclusion that my wort is poison. Not a sliver of CO2 has been produced. First yeast did produce heat in the wort for a day, but no CO2. Tried heating the wort, agitating and all, but it remains dead.
Some little changes in my process were made – 18 liters instead of 19 for mashing so that I could fit 900 grams extra malt in, and strike temperature up by one degree to 72 °C due to less water and more grain. Tomorrow evening I'm going to have to dump 20 litres of fine wort down the toilet and plan another brew day. Damn, this loss hits like having to bury a pet...
A pity I can't throw you a tube of yeast this fast! Good luck!