I think it is just specifying A time, not saying that that is the current time, so Duo doesn't like your "It is" before the time expression. I also think you might need a space before the "am" to separate it from the 8:45.
It happened several times. I answered exactly the same as your correct solution but rejected. I don't know why.
If previously I answered using Microsoft Pin Yin, this time I answered using Windows keyboard.