Could be a couple reasons.
If you are logged in to your account on other devices, the verification code will go the Telegram app there instead of SMS.
If you aren't logged in other places and the SMS code isn't delivering, please DM me your phone number and cell service provider— Telegram Messenger (@telegram) December 13, 2019
#telegram
If you are logged in to your account on other devices, the verification code will go the Telegram app there instead of SMS.
If you aren't logged in other places and the SMS code isn't delivering, please DM me your phone number and cell service provider— Telegram Messenger (@telegram) December 13, 2019
#telegram