macOS network extension - activate vpn provider failed on startVPNTunnel - swift

Question

I'm trying to start the vpn provider from a container application
After I successfully activated the extension, and started the process by sending xpc request to the network extension, I've tried to load the provider and start getting notifications about handleNewFlow
I use the following callback to signal process has started, in order to start the configuration phase.
extension NetworkExtensionManager: OSSystemExtensionRequestDelegate {
...
func request(_ request: OSSystemExtensionRequest,
didFinishWithResult result: OSSystemExtensionRequest.Result) {
...
After loadAllPreferences, I've set the manager from which I'd like to load the provider:
NEAppProxyProviderManager.loadAllFromPreferences { [self] (managers, error) in
assert(Thread.isMainThread)
if let error = error {
print(error.localizedDescription)
} else {
let manager = managers?.first ?? NEAppProxyProviderManager()
let proto = (manager.protocolConfiguration as? NETunnelProviderProtocol) ?? NETunnelProviderProtocol()
proto.serverAddress = "myHost"
proto.providerBundleIdentifier = "myExtensionBundle"
proto.providerConfiguration = ["key": "val"]
manager.localizedDescription = "myApp"
manager.protocolConfiguration = proto
manager.isEnabled = true
Then I extract the connection out of the manager and use it to start the tunnel provider (hopefully this operation will create a new item under System Preferences --> Network)
let session = manager.connection as! NETunnelProviderSession
do {
os_log(" manager.connection status: \(session.status.rawValue)")
try session.startVPNTunnel(options: nil)
}
catch {
os_log("failed to initProviderManager app proxy provider, \(error.localizedDescription)")
print(error)
}
However, I've got the following error message from the exception thrown out of this line session.startVPNTunnel :
failed to initProviderManager app proxy provider, The operation couldn’t be completed. (NEVPNErrorDomain error 1.)
Looking for the error name I found this NEVPNErrorConfigurationInvalid
Perhaps you can help me figure out where I go wrong in my attempt to start the tunnel provider ?
Thanks !