If your SMS verification code isn't arriving, try these steps in order:
Check your signal and wait a moment. SMS codes usually arrive within a minute or two but can be delayed by network congestion. Make sure you have a strong signal, then give it a short while before requesting a new one. Toggling Airplane Mode on and off can help your phone re-establish a connection.
Request the code again. If nothing arrives, request a new code—always use the most recent one, as older codes stop working.
Try receiving your code via WhatsApp. If SMS isn't coming through, you can opt to receive your code on WhatsApp instead. See How to receive RedotPay verification codes via WhatsApp. Make sure you're logged into WhatsApp on the number registered to your account.
Update the RedotPay app. Confirm you're on the latest version, as an outdated app can occasionally cause issues.