Routing for DNS Connectivity

Our school, The Island School, recently signed up for your service. Our IT company has been unable to get the routing for DNS connectivity to direct requests to NextDNS and have our filtering work. Here is what they have done so far:

1. Puchased and configured a static IP address from our internet service provider, Comcast. Set the DNS entry for the ones provided in our NextDNS account.

2. Configured DNS on our LAN subnet to use the same DNS servers as our Unifi UDM-Pro firewall

3. Installed the NextDNS app on our UniFi UDM-Pro firewall using the provided commands after SSH login into the device. Verified the service was activated.

 We have installed the Apple OS app on one MacBook laptop and it does successfully block the content we have setup in parental controls, but would prefer using the linked IP and DNS entries to filter all traffic on our network, but are hitting a road block. Any help would be greatly appreciated.