@User i see a small gap between vdd symbol and the net. Ensure they are connected. Move the

save all

line before the

tran

line, place a voltage source for VDD:

VVDD VDD 0 dc 1.2

Add this line to the 'NgSpice' symbol or place a vsource symbol in the schematic. If you want the xschem 'Waves' button to work, the raw file must have the same name of the circuit. So I assume your schematic is CLK_TEST.sch. Otherwise change the

write

line accordingly. Also you should better use 1.8V instead of 1.2V, sky130 low voltage transistors are tuned for 1.8V operation.