In the poker tournament, I had a bad feeling, but it wasn’t possible for me to fold my hand.
You already know how 可能 means possible. So when you add not it becomes impossible.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well. It will help to know how to read 可能 first as well.