Here's how:

1.  Windows Defender Antivirus

1.1: Please follow these instructions to add exclusions for Lumion in Windows Defender Antivirus:

For the list of exclusions see this article section 1.3:

• Knowledge Base:  How do you resolve anti-virus and firewall problems?
  
  
• External Link:  Add an exclusion to Windows Defender Antivirus

1.2:  Reboot your PC after adding the exclusions.  This is important to enable the changes.

2.  Windows Defender Firewall

2.1: Then type 'Allow an app through Windows Firewall' in the Windows Search field and press Enter:

2.2: Click on 'Change settings':

2.3: Please click on 'Allow another app...':

2.4: In the window that appears, click on 'Browse' and select 'Lumion.exe' in the folder you installed Lumion in.

The default location is: C:\Program Files\Lumion (Version)

2.5: Click on the 'Add' button: