I recently configured my lab DNS infoblox server in a grid and setup some authoritative forward-mapping zones on it for my lab web-servers;
The DNS queries for the authoritative zones were working fine;
I then configured the DNS grid with 188.8.131.52 as a forwarder;
But the recursive queries were getting refused;
This happens because, by default, the DNS grid is configured to deny any recursive queries that is received;
After allowing recursive queries from my source subnet, DNS grid started resolving google.com;
When adding a forwarder in your infoblox grid, ensure recursive queries are allowed as well. They can be allowed for any subnet, in my case since it is a lab setup I restricted it to just 192.168.1.0/24 for test purposes.