Fortinet does not resolve hostname

[josecoca]

My firewall does not resolve hostname, does anyone know how to tell me the possible causes?

Example with hostname: 

Example with IP from hostname:

[gfleming]

Can you resolve the FQDN? vm-ad01.yournetwork.com, as an example.

If so, then you need to add your domain as a search suffix:

config system dns
 ...
 set domain "yournetwork.com"
 ...

If it does not resolve for FQDN then you probably need to add your internal DNS servers to your FortiGate's DNS config

config system dns
  set primary <internal dns IP>
  set secondary <internal dns #2 IP>