I originally thought that something was missing on my brand new demo board.
I fooled around with it, and it went "pop" and moved well forward.
Are you pulling up so that the pedal rotates on that pin toward the back of the board BEFORE you try to move it forward.
I think that was the secret.
Kind of pull back and rotate up, then slide it forward and it should pop into place to release the mast foot car.
Unfotunately it's not real "sailor friendly" on the water, until it gets used alot and frees
Hope this helps,