There might be times when there would be a delay in receiving the OTP.
This normally happens due to the network issues of the telecom service being used.
If you are facing such an issue, you may try switching on the Airplane mode and switching it off again.
Also, if you do not have any number already registered, you can try with a different number or if the number is already registered and you are not being able to login with OTP, you may login with your email ID and password for the time being.