Can't get Pi-hole working, dns won't resolve

[Techloid-g]

Been trying to get Pihole working for a few days now, followed all the steps several times and still nothing. My devices will read that they have the right DNS address and will load pages but pi-hole doesn't filter. Go to the setting page and there tons of cashed DNS insertions but 0 evictions. Perhaps there is some coding I have to do to the router to make it the only DNS? if I do an nslookup on a device I'll get :

Server:  raspberrypi
Address:  192.168.1.84

DNS request timed out.
    timeout was 2 seconds.
DNS request timed out.
    timeout was 2 seconds.
DNS request timed out.
    timeout was 2 seconds.
DNS request timed out.
    timeout was 2 seconds.
*** Request to raspberrypi timed-out

Router is Asus RT-AC87R

Any help appreciated.

Expected Behaviour:

DNS filter working
-raspbian buster
-raspberry Pi4

Actual Behaviour:

DNS not filtering

Debug Token:

yc38k6zfj8

[DanSchaper]

Try a dig pi.hole and see if you get back the IP address of the DNS server you wish to use.

[Techloid-g]

Yeah it's reading as cloudflare server on my devices

[jfb]

Those devices are not using Pi-hole for DNS. This is likely a router setting.

[Techloid-g]

It's reading as cloudflare on my devices from the outside. On the devices themselves it reads as the ip of the pihole server and my router. I assume it is the router but I don't appear to have options to disable the router from advertising it's own ip in addition to user specified, or forwarding local domain queries to upstream DNS.

[Techloid-g]

So installed Merlin firmware on router to enable options and I no longer get the router's IP as an additional DNS, but I'm still not getting any filtering and dig still shows the wrong dns server.