This problem happens on iOS system.
This problem occurs in multiple models and multiple systems, not in a specific iOS system or phone model.
I've found several similar questions on the Apple Developer Forums, but none seem to have a final solution.
Similar problem:
VPN not starting:
https://developer.apple.com/forums/thread/678399
NEPacketTunnelProvider Cannot Be Started
https://developer.apple.com/forums//thread/729069