The production you are working on will invite you to CrewStart.
If you have not received a verification code through when going through the invitation email then this may be down to your mobile number being entered incorrectly on the CrewStart application. If you are not receiving the verification code through you will need to contact the production you are working on directly.
They will then check the number that has been entered into the system and update if necessary, once they have updated this they will send you through a new invitation link so you can receive the verification code.