Mr. caj4isu is on the right track. When you disconnect your loader, you're left with a 2 foot long "pigtail" with a female quick connect at the end, and 2 vacant quick connects, one male, one female.
You need to connect your female "pigtail" with the male (middle) vacant quick connect. Since you've run your tractor without it connected, you may have resistance to the connection because of residual hydraulic pressure. Take a screwdriver and carefully depress the nipples in the quick connects WITHOUT the tractor running to relieve this residual pressure. Then make your connection.
Male. Female. Nipples. Next time, we'll talk about shafts and receiving units. My wife hates 'gender correctness' when I'm talking about fittings. Just uncomfortable with it for some reason.