SimSmsBox Short answer: First decide whether you typed a captcha, an SMS code, or an authenticator code. The same error string has three unrelated causes, and retrying the wrong one never helps.
Thirty-second triage
| What you typed | Tell-tale sign | Go to |
|---|---|---|
| Distorted characters or a puzzle | There’s an image with a refresh button | Type 1 |
| Digits from a text message | Countdown and a resend button | Type 2 |
| Digits that change every 30s | No network needed, circular timer | Type 3 |
Type 1: captcha
Usually a session or state problem rather than a typo:
- Case sensitivity, plus the
0/Oand1/ltraps. - Page sat open too long — the server-side challenge expired. Refresh the image and retype.
- Cookies blocked or cross-site restrictions, so the server can’t match your session.
- Multiple tabs: a later tab regenerated the challenge and invalidated the earlier one.
- Can’t read it? Get a new one instead of guessing. Background: what is CAPTCHA.
Type 2: SMS code
One rule dominates: only the newest code is valid.
- If you tapped resend, use the last message that arrived.
- Past the validity window (usually 5–10 minutes) you must request a fresh one. See why OTP codes expire.
- Already used it once? One-time means one time.
- Changing phone number or device mid-flow kills the old code.
- Watch for pasted whitespace, or grabbing the wrong digits out of the message.
Never received it at all? That’s a different problem — see SMS code not received.
Type 3: authenticator code (TOTP)
Nearly always clock drift:
- The phone’s time is set manually and is tens of seconds off.
- Turn on automatic date and time, restart the authenticator, retry.
- After migrating devices, you may be reading a stale entry or a duplicate with the same name.
- Details: authenticator code not working.
Still failing after all three
- Switch networks to rule out a proxy or corporate gateway rewriting the request.
- Try a private window to rule out extensions.
- Too many wrong attempts may have locked you out temporarily. See too many verification attempts.
- Using a rented number? Confirm the service matches the app first — see why the SMS platform isn’t receiving the code.
Wrap-up
Classify, then act. Captchas are about session and freshness, SMS codes about newest-and-unused, authenticator codes about the phone clock.