I had a similar experience. I invited a friend and didn't receive anything at first, so I thought it wasn't working. Then, after doing some research, I realized that it doesn’t happen instantly. It's important that the person not only signs up but also logs into the game and spends some time there. I play on the Sportino website. They have a sportzino referral bonus, and after my friend played for a while, I received some coins. The amount isn’t huge, but it's a nice bonus. As I understand it, this measure prevents you from creating multiple accounts and receiving endless benefits through the referral program. I had to nudge my friend a bit because he kept forgetting my request. Now, we both play slots there and even stream our gameplay to each other via Discord from time to time.