Go on the Basic details page.
Caseload history.
If has a caseload history the text message will to that person listed.
If there is no caseload history, go to interaction page to the significant contact for that person which has to be "yes" if it is "no" you will need to configure it to "yes". Then the YP text message should go to that person.
How to change significant contact from N to Y.
Lookups LU_INTERVENTION click in the description (edit pencil icon) you want to change i.e. Email/text/Letter.
Significant contact check box ticked it and will show as Yes on the intervention page.
Young person can be added to user caseload via User tools, how to add caseload will be on the CCIS user guide.