DIAGNOSIS The Rapid Cold Brew function works by super-saturating the grounds with cold water. Weak brew usually means the grind is wrong or you're not using enough coffee.
FIX You gotta treat it differently than hot coffee. 1) Use a coarse, dark roast grind—like for a French press. Pre-ground drip coffee is too fine. 2) Pack the brew basket firmly. Use at least 2 full tablespoons per serving, maybe more for your taste. 3) Make sure you're selecting the Cold Brew function (the snowflake icon), not just the Over Ice setting. The machine runs a longer, slower cycle for cold brew.
IF THAT DIDN'T WORK Check that the spray head inside the basket area isn't clogged with old grounds or mineral deposits. Run a water-only Cold Brew cycle and look up inside—you should see a steady, wide spray, not a dribble.
HEADS UP The Cold Brew function uses a different pump and pathway than the hot system. If you haven't used it in a while, the first few seconds might sputter as it primes—that's normal.