I'm trying to charge printing to a grant but I don't see the Cost Center Selection window.

If you only see the window asking if you want to use your C-Card funds, not the window to select a grant or department, this means either that you are not an authorized grant/department user OR that the grant/department is out of funds. The Principal Investigator or signature authority on your grant/department needs to create a Help Desk Ticket [1] to find a solution to this problem.