Slow-fermented bread doesn't rise
UPDATE: recently I started using drier starter with bread-dough like consistency and add it when it's about room temperature. Measuring the ingredients precisely also helps, provided you figured out the proper ratio of flour and water.

My solution: simply use more starter. Generally the starter is kept in the fridge in a jar. I take out the jar from the fridge, add around 150g of flour and 150ml water. After an hour or two, once there are bubbles on the surface, I just add around 300g of this mixture to the bread. The jar (with little starter left) goes back to the fridge. The