If she's mad, your Tamagotchi characters are too young. They can begin using the dating channel 48 unpaused hours after becoming adults.
If she's sleeping, you've already used the dating channel the maximum number of times (3) that you can use it in one day. Try again tomorrow. Or... adjust the clock so your Tamagotchi characters go to sleep, then adjust it again so they wake up, then try the dating channel again.