This can happen for a few different reasons:
Not washed before used: UpAiry Underwear should be washed 2-3 times before use to prepare the fabric to absorb liquid.
Improper fitment: This is the #1 reason. Ensure there are no gaps between the legs and waist.
The pee wasn't absorbed: For UpAiry Underwear to be leak proof, the liquid needs to come in contact with the leak proof layers (see picture above). If the liquid goes through the top part of the Training Pants, it will go through.
Too much liquid: UpAiry Underwear absorb quite a bit of liquid, but often if its a large pee, a little bit may leak out.
If this is consistently an issue, reach out to us! We want to make sure you are happy with out product!