Sour coffee is under-extracted coffee. The water didn't pull enough out, and the acids showed up without the sugars to balance them.

Grind finer first

The biggest lever is grind. A finer grind means more surface area, more extraction, less sour. Nudge it one notch and taste again.

Then give it time

If it's still sour, let the brew run a little longer — a 3:30 pour instead of 3:00. Change one thing at a time.