Check the four mounting screws of your cleats. If they're too tight, they will bind the C-clip spring and make it harder to engage/release. Also, like many clipless pedal cleats, Speedplays take some time to break in. One way to accelerate this is to spend about an hour repeatedly clipping in and out. Bring your bike into your living room, position it next to a wall or doorframe, turn on the TV and while using the wall to steady yourself, just clip in and out for about an hour.