OPG/MOO orders being canelled

Hi, I am a newbie trying to test a certain strategy on my paper trading account. I queued up several OPG market sell orders last night and noticed this morning that the majority of them did not fill and got cancelled right away at the market open. Can anyone explain why this is happening? Is it possible to queue up regular day and opg market sell orders together to ensure that at least one of them executes?