Whitelisting devices not working

Hello,

I have trouble whitelisting devices, so that PiHole is not filtering their traffic.

https://tricorder.pi-hole.net/taLdUTNg/

I have a Fritz Box as router. Configured in the Fritz Box. that the DNS is coming from the PiHole devivce with the IP 192.168.2.2.
Added in PiHole a new group called Whitelist.
Added devices by IP to that group.
Made sure that those devices where removed from the default group.
Activated the Whitelist group.
And still PiHole is blocking those devices.

I found a similar topic Whitelist Devices from Pi-Hole - #14 by Bucking_Horn
which has this remark

See our Group Management docs, specifically Example 1: Exclude from blocking. Note that client-based filtering is only possible if your router distributes Pi-hole as local DNS server (as opposed to your router distributing its own IP as local DNS and only using Pi-hole as its upstream).

But I don't understand this correctly. The Fritz Box offers me an option to configure the DNS for my network, which I set to the IP of the PiHole. Should this not be correct? But why does whitelisting not work in this case?

Ok solved it by selecting a known devices from the drop down list. Just entering the IP does not seem to do the trick.