Verification and compatibility

Why did my verification code not arrive?

Answer

Four causes account for nearly all cases. The number was entered with its domestic trunk zero instead of E.164 format. The service rejects that range outright. The message got filtered as application-to-person traffic between sender and destination. Or the code is queued behind a rate limit you triggered by requesting repeatedly. Check the format first; it is by far the most common. Requesting five more times worsens the other three.

The longer version

Each symptom points somewhere specific. "Invalid number" means format or an outright range rejection, so re-check E.164 and then try another country. "Number already in use" means the line was recycled and a previous holder registered, which a never-recycled number fixes. No error and no code at all is the signature of A2P filtering, and changing destination country usually clears it, because the filtering lives on a route rather than on your line. A code that arrives late is aggregator queueing at peak: request once, wait two minutes, and resist the urge, because most services invalidate earlier codes and start rate-limiting when you hammer them. If none of it resolves within 24 hours of activation, that is what the refund window is for.