First of all, where did you get the seed from? Like citrus, Poncirus seed needs to be fresh from the fruit or stored correctly in cool conditions around 35-40F. Dry seed at room temperature rapidly loses viability.
Seed germinates in about two weeks if kept around 70-80F. Cooler takes longer and there is then a danger of rot setting in.

Here is a link that might be useful: Poncirus info

I got them off a seller on ebay.

I have found the following process works every time for me
store seed at 40F for at least 30 days... then LIGHTLY cover the seed soil temp for germination 60-75F & takes 21-28 days to germinate
REAMBER a another name for this is "Hardy Orange" not tropical orange

I sealed my remaining seeds in a plastic bag and put them in the refrigerator. Hopefully that will keep them from going bad.

Depends whether the seeds you bought were fresh from this years fruits, or stored from last year.
When did you sow them, and at what temperature?

I sowed them on 9/18 and the temperature is about 20 degrees Celsius.

I pealed the skin coating off 4 seeds and planted them in a rigid lunch meat container with its lid on to hold in moisture, in a sand compost mix. They came up in 8 days. They are real sensitive to stem rot at the soil surface. I separated them to there own pots an watered them from underneath in a bucket of tap water (chlorinated) so the soil surface and stem never get wet. These plants NEED iron zinc and manganese. these are my 4 P.T's after 7 months. good luck