X_NOTIFY_SMS_TRANSPORT_MISSING
Means
an SMS was sent with no SmsTransport installed
Typical cause
smsChannel() delivered outside development and test, and apps/<app>/runtime.ts names no smsTransport — the memory transport would swallow the message, so the send is refused instead
Fix
add smsTransport: yourTransport() to apps/<app>/runtime.ts — behavesLike(smsTransportConformance, () => yourTransport()) proves it