I put "Mowimy po polsku i angielsku" which came back as incorrect. I see that I messed up the "ó" in Mówimy. But, did I also get it wrong because I excluded the second "po". In this situation am I required to say po twice?
No, you are not required, it should be accepted, although it is probably colloquial not to repeat "po" in this structure.
It is accepted (at least now)