Look for burnt connectors in the backbox. Probably in the center near the bottom. Marco Specialties or Bay area amusements will have the drop targets & decals. Welcome to pinside!

9 out of 10 your power supply has bad connectors and pins. Known problem. You will need to re do the whole GI section of the power supply if thats the case.. Connectors and pins. Also check the solders on the PPB board as it will have some bad solders at the very least!
Post a picture of your backbox or at least the power supply board and the PPB board and any burnt pins and I would be glad to walk you through it. Also check fuses with a multimeter out of circuit!
Also next most common failure is the fuse holders! Try to depress the fuses down hard and if the fuse holder splits apart or spreads easily it needs to be replaced. Only get the good quality ones from your parts store.

Yes, check your fuse holders should be the problem. Good luck with your 1st pinball. After you have one you have to have another and then another. What a great hobby!!

I had to replace several burned connectors on mine to get the backbox lights and all the playfield insert lights working and the upper GI lights also working. I just bought the replacement connectors, along with the molex insertion tool to easily push the wires into the connectors. Was lucky I didn't have to also replace the board pins, so try the connectors first and see if that resolves the issue. If not, then go ahead and replace the board pins for the connectors.