Issue with users not receiving OTP

[iangrundy]

I'm involved in a web app that uses tdLib to authorise Telegram users. I've worked users through the onboarding process. Some users do not receive the OTP from Telegram.

I have confirmed the phone numbers are correct, and sent in the correct format. In the application logs, successful and failed cases look identical. Real errors are being logged - eg. When Telegram returns the PHONE_NUMBER_BANNED exception.

In all cases I can see the authorization States passing from AuthorizationStateWaitTdlibParameters -> AuthorizationStateWaitPhoneNumber -> AuthorizationStateWaitCode.

Are there any other factors that anyone is aware of that would result in the users not receiving the OTP from Telegram?

[levlam]

It is up to the server how and when authentication code is sent to the user. App can't control this behavior.

[iangrundy]

That makes sense and is fine in principle.

In cases where it works, the OTP appears within like 2-3 seconds. I've not encountered it showing up 10 minutes later. It either seems to work immediately, or not at all. Which makes me think that there is some factor I am missing.

[levlam]

The delivery time may vary, but the user can't affect this anyway.