Pattern overlay hides actual layer

Hello, having an issue with my effects. on a single layer i have a rectangle that is colored in blue. when i add a pattern overlay (diagonal lines) to the same layer as the rectangle, it covers the blue rectangle and all that is visible are black diagonal lines on a white background. Normally this would give me black diagonal lines on the same blue background as my rectangle. Any clue why this effect no longer applies correctly?

thanks in advance for any help