Since the error is specifically ipAddressNotInSpecifiedRange, this is almost certainly an environment or tenant network policy issue rather than a problem with Power Apps or the VPN client itself. The next step is to have your Power Platform administrator verify the environment's IP restrictions and your Entra ID administrator review any Conditional Access policies based on network location. In most cases, adding the VPN's public egress IP address (or IP range) to the allowed list resolves the issue.
