Hopefully, I can remember correctly, but quite a few years since I sold mine:
There is an on/off switch on the power supply.
Try plugging both the power supplie's cords into the power strip and turn the switch on.
If that works great, go on to checking the timer with a regular household lamp.
If the timer works, then connect the timer to the power strip, and the power supply to the power strip and timer. Then run the timer and see if it works. Note that most timers have a "Enlarger" and "Safelight" receptacle and use the "Enlarger" one for the power supply cord that says from timer.
Jon