Commissary access does not open up the moment someone walks through the door, and that applies to phone calls and visitation as well. Everything is on hold until orientation is complete.
When an inmate arrives at a reception or evaluation center, the facility's first priority is processing, not comfort. That means medical screening, classification interviews, housing assignment, property inventory, and orientation to the rules and expectations of the institution. Until that process is finished, no privileges are extended. It is not personal and it is not punitive. It is simply the order of operations every new arrival goes through regardless of their offense or background.
Orientation typically wraps up within a week, though some facilities run longer depending on their intake volume and staffing. Once it is complete, commissary access opens up along with phone privileges and the ability to add names to the visiting list.
The practical advice for anyone sending support is to get money on the account as early as possible so funds are sitting there and ready the moment access becomes available. There is sometimes a processing delay between when money is deposited and when it shows up as available in the account, so getting it in early means your inmate is not waiting on both the orientation period and a deposit to clear at the same time.
A letter sent during that orientation window is still worth doing. Mail continues to move even when other privileges are suspended, and having something waiting for them when orientation ends is a good way to start the next chapter on a positive note.