Fritz!Box parental controls

I have a Fritz 3370, trying to use the parental controls feature to block youtube access for a particular Chromebook.

I created a new access profile for this Chromebook specifically, and assigned it a permanent IPv4 on the network.

The profile is:

- Online time: unlimited

- Shared budget: no

- Filters: blacklist

- Blocked applications: none

I then added youtube.com and https://www.youtube.com to the blacklist.

Outcome: my darling daughter can still watch youtube on her Chromebook at will.

The Fritz definitely recognises her Chromebook, and supposedly applies the right access profile, it's just that the rules don't seem to be working. Would appreciate any ideas here.