Hi @bluemoon61,
Instead of using the Layer 7 settings, try to use the Blocked website categories option under Security appliance only just below the Layer 7 settings. Choose the Social Networking as Facebook, Snapchat and Instagram falls into this category. You can also block other categories if you want.
![Cmadiam82_0-1606546611165.png Cmadiam82_0-1606546611165.png](https://community.meraki.com/t5/image/serverpage/image-id/15683i49F42F8533505E04/image-size/medium?v=v2&px=400)
Hope it helps.