Two mistakes here.
Between pins 1-8 and 5V measures 0 V
I did not told to measure in this way. Basically you are measuring between 5 V and 5 V, it won't give any voltage obviously because there's no potential difference.
What I told was:
measure the voltage between pins 1-8 on socket and GND
Between pins 1-8 and GND (pin 9) it should give around 5 V as I told before.
As I told here
with ULN connected the voltage should be around 1.5 V.
After can you measure the voltage between 5 V and pins 11-18 on socket with PCF signal HIGH? It should be around 5 V too.
Here my question is incomplete. I forgot to say to put the ULN back on socket before measure.
Without ULN the socket pin is connected only to DB25 and it will give 0~1 V only.
With ULN connected
between pin 11-18 should give around 5 V as I told before.
This test is not needed and will make the things more complicated here.