Not likely but possible. Check the simple stuff first. Most likely the flippers and slingshots are separate problems. Check flipper power supply board (it has it's own fuse F2, small board under CPU board). Special solenoids get power from main power supply board (also F2, but to the right of the CPU board)

Verify power present at both terminals of the coils of the flippers and slings with a meter.
From there it's test the actuating switches.

Once you get all that looked into then report back with specifics.

You should hear the K1 relay click in when the game is started or when you enter test mode.

Measure from the flipper button org-gry or org-vio wire (ground side of the button) back to chassis ground (ground braid is convenient). If K1 is working you should have continuity to ground. Current path: power supply-->flipper coil-->>cabinet button--->>back to CPU K1 --->>to ground

Just took a look at the MPU schematics, if relay K1 is found to not be pulling in it looks like U50 IC is feeding into both Q7(turns on K1 flipper relay) and special solenoids SS5T and SS6T. I'm not sure if these are the for the slings or not. Grounding Q77 or Q79 should tell you if those are the correct transistors for the slings. If U50 is bad that could be the common fault between flippers and slings.

Wow, and it wasn't even bad. Good for you - glad you got it!