One spout is blocked. Clear it now.
Fix: Use a toothpick to gently clear any coffee grounds or residue from the blocked coffee spout.
If that didn't work: The internal pathway for that spout might be obstructed. Run a rinse cycle by pressing the rinse button with no cup in place to see if water flows from both spouts.
Prevention: Regular cleaning of the spouts and running rinse cycles helps prevent this. Never use tools harder than a toothpick to avoid scratching the spouts.