How can I solve PRTG on Fortigate error?

I configured SNMP traffic on the Fortigate WAN interface for PRTG, but I get the error:  "No response (check: firewalls, routing, snmp settings of device, IPs, SNMP version, community, passwords etc) (SNMP error # -2003)"

First of all please check if the SNMP Settings (Version, Community String, port, eventual authentication, etc.) are correct. Then please also check if PRTG (or the PC on which PRTG is installed) is allowed to send SNMP Requests to the device in case (this usually has to be allowed on Firwalls). You can also use our SNMP Tester to test the SNMP-Functionality on the target device(s). For example reading the Device Uptime should definitely be possible. 

The SNMP Port can be set on the "Settings"-tab of the device in PRTG under "SNMP Credentials".

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The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.