Grind setting is too coarse, or the grinder burrs are worn. The coffee puck isn't creating enough resistance.
Fix: Turn the internal coffee grinder adjustment knob to a finer setting. It's inside the bean hopper. Turn it toward the "+" symbol. Clean the brew group. Remove it, rinse under warm water, and dry thoroughly before reinserting.
If that didn't work, the pump (part 5113211291) may be failing and not building proper pressure. Descale the machine. Limescale buildup in the internal tubes can restrict water flow.
Heads up: Use only dark roast beans for a stronger taste. Light roasts will produce a thinner coffee regardless of settings.