I don't receive a confirmation code in Telegram/WhatsApp, what should I do?

If the code is requested in the Telegram messenger, check that the search for other contacts by phone number is available, to do this, go to Settings > Privacy > Phone number > in the Who can find me by phone number section > Select the All item, also make sure that all users can send you messages. The code comes from the official Telegram bot @VerificationCodes.