To address the issue, do the following:
- Open the IIS Manager (inetmgr) on which the Apex One server is installed.
- Click Apex One server hostname.
- Double-click on the IP and Domain Restrictions icon in the IIS section.
- Check if the IP address is in the Deny Entry list. If exists, select the IP Address then click Remove.
- Click on the Edit Feature Settings... in the Actions pane.
- Check if the "Access for unspecified clients" is set to Allow.
- Restart the IIS Admin Service.
If the issue persists, please contact Trend Micro Technical Support.