I am unable to discovery the fortigate 60D services i am using the RAW 1.6.0p7 version

Cookbook for the FortiGates:

https://docs.fortinet.com/document/fortigate/6.2.3/cookbook/547825/snmp-v1-v2c-communities

impotant are the security levels for the user:

https://help.fortinet.com/fos50hlp/54/Content/FortiOS/fortigate-system-administration-54/Monitoring/SNMP.htm