Using vivado on Pynq-Z2 board without PS

If you are using the PL “Ethernet” clock (H15), this clock is unstable unless an Ethernet cable is plugging in.

There is no “reset” pin connected to the PL. You could use one of the 4x pushbuttons, or one of the 2x switches which are connected to the PL. You would use this as the reset input in your PL design.