Complex corporate networks often have strict firewall rules that block outbound traffic to non-whitelisted domains. Even if a machine has internet access, it may be blocked from reaching the vendor's licensing servers due to strict ingress/egress policies. An offline license bypasses the need to reconfigure firewalls or open specific ports for activation traffic.
Offline licensing is generally restricted to RealVNC Connect Enterprise subscriptions . How to Obtain an Offline License File vnc offline license file
File was modified (even saving it again in Notepad can add a Byte Order Mark). Fix: Re-download the file from the RealVNC portal. Copy it using robocopy or rsync rather than drag-and-drop. Complex corporate networks often have strict firewall rules