If Instagram detects unusual behavior (e.g., logging in from a different country, rapid liking, or automated tools), it will lock the account until you provide the verification code.
Many users forget that they linked an authentication app (like Google Authenticator) months ago. If you select "Send SMS" on the login screen but don't receive a text, it might be because your primary setting is the Authentication App. Check your authenticator app to see if the code is sitting there waiting for you. 6 digit code for instagram
If you tell your web browser to "remember me" but then delete your cookies, Instagram forgets your device. The next time you try to log in, it will request the 6-digit code. If Instagram detects unusual behavior (e