You might see an Apache 403 Forbidden Warning error reported in #Nagios after a new installation or upgrade to OES 2018 or later.
To resolve the issue, you can try the following:
- Log in to the #server as the root user, open a terminal console.
- Then navigate to the /etc/nagios/objects directory.
- Restart Nagios.
More info >>
https://ibmimedia.com/blog/75/solution-to-nagios-access-forbidden-error-403
