Every new or incoming inmate goes through an orientation period before phone and visitation privileges are activated. This process typically takes about a week, though it can run a little shorter or longer depending on the facility's intake workload and scheduling.
During that window, the inmate is getting classified, processed, and briefed on the facility's rules and programs. Phone access, visiting lists, and commissary access all get set up as part of that orientation, not before it.
If you have not heard anything for the first several days after your person was placed, that is the most likely explanation. Keep watching the state DOC inmate locator to confirm their placement if you do not already have the facility name, and send a letter as soon as you know where they are. Mail typically reaches inmates even during the orientation period, and a letter with your phone number and contact information gives them what they need to call you the moment their phone access opens up.