A missing verification text can mean the number is ineligible, the carrier has not delivered the message, or the service has temporarily limited requests. Those are different problems. Buying another random number before reading the error can leave you paying twice without solving any of them.
Claude’s number requirement
Claude’s verification instructions require a number from a supported location and exclude VoIP, Google Voice, app-generated numbers and landlines. This is more specific than “a number that receives texts”. Check the service’s location policy before choosing a carrier.
A travel eSIM that sells only GB of data is not a replacement for a mobile number with SMS. If a seller advertises a “US eSIM”, read whether a US telephone number and incoming texts are actually included, where activation is allowed and what it costs to keep the number.
For Codex, identify the sign-in route first
Codex authentication supports ChatGPT sign-in and API-key sign-in for local clients. These are not interchangeable registration instructions. Follow the prompt in your chosen account; do not assume a phone-number requirement from a different product or an old API tutorial applies to you.
If an eligible number does not receive the code
- Check the country code, digits and whether that line receives an ordinary text. Confirm it is active and connected to a network if you are roaming.
- Wait for the on-screen resend interval. Use only the newest code when several messages arrive.
- Ask your carrier about blocked service or international texts. Then send the app’s support team the error, time, country code and carrier name.
- Keep the number under your control if the account uses it for later checks. A rented one-time code does not provide future recovery.