Make sure your timing library has k-factors defined so the tool knows how timing should be scaled based on PVT. For example, the timing constraint equation for setup rise is.
rise_constraint * (1 + delta_voltage * k_volt_setup_rise)
* (1 + delta_temp * k_temp_setup_rise)
* (1 + delta_process * k_process_setup_rise)
Hope this helps!
- Brian