Sidecar;

I recently updated my macboook air (2017) to the macOS Catalina and I took the tour it gives and noticed the sidecar option that allows me to use my iPad 7Gen (it is updated) as a second display but when I go to the airplay icon on my sidebar it says "Off" so I went to the system prefrences and it where it gives the option of Airplay Display I only get the " no" option. what can I do? I've tried looking into the firewall but nothing seems to be working at all.