Account Activation: If the code is correct, your account is activated, and you can proceed to set up your profile (name, username, profile picture).
2. Logging in from a New Device:
The process is very similar to initial registration:
Enter Phone Number: On the new device, you enter your registered phone number.
Verification Code Sent: Telegram sends a telegram number database verification code.
Preferred Method (In-App first): Telegram prioritizes sending the code to your active Telegram sessions on other devices. This is a security measure, as it means someone trying to log into your account from a new device would need not only your phone number but also access to one of your currently logged-in Telegram instances.
SMS/Call Fallback: If you don't have any active Telegram sessions, or if the in-app delivery fails/isn't preferred, Telegram will fall back to sending the code via SMS or offering a voice call to your registered phone number.
Enter Code & Login: You enter the code, and the new device is logged into your account.
3. Role of Two-Step Verification (2FA) in the Process:
Added Layer of Security: If you have Two-Step Verification (2FA) enabled (highly recommended!), the phone number verification process is followed by an additional step.
Password Required: After successfully entering the SMS/in-App/call code, you will also be prompted to enter your 2FA password.
Protects Against SIM Swap: This is critical. Even if someone gains unauthorized control of your phone number (e.g., through a SIM swap attack) and can receive the initial verification code, they cannot access your Telegram account without your 2FA password.
Incorrect Number: Double-check that you've entered the correct phone number and country code.