Most likely, you have setup your Pi-hole as your router’s upstream DNS.
While this filters all DNS traffic in your local network, Pi-hole will see all DNS requests as originating from a single machine: your router.
DNS queries will travel like this, e.g.:
Laptop -> Router -> Pi-hole -> Pi-hole's upstream DNS server
Smartphone -> Router -> Pi-hole -> Pi-hole's upstream DNS server
To change this, try reconfiguring your router to
- use local DNS-resolution (required)
- disable upstream DNS resolution (optional)
By handing out Pi-hole as local DNS server to your clients, they will ask your Pi-hole directly, allowing Pi-hole to see the correct origin of DNS queries.
DNS queries will travel like this, e.g.:
Laptop -> Pi-hole -> Pi-hole's upstream DNS server
Smartphone -> Pi-hole -> Pi-hole's upstream DNS server
If your router does not offer diverting DNS to a local DNS server, you can configure each device manually to use Pi-hole as DNS.
The forum may have advice on how to do setup local DNS resolution with your specific router model, try searching for your router model.
As starting point, refer to How do I configure my devices to use Pi-hole as their DNS server?