Looks like the solenoid power got shorted somewhere.
I have to ask, are those 20 amp fuses in F4 and F6 ?

First thing to do is disconnect any burnt/melted out wires at each end and find out where the solenoid power short originated from. Did any wires running to/at the playfield suffer any heat stress (melt)?

Unfortunately you still don't know if the transformer winding for solenoid power suffered any damage from the excessive current short - some of the internal winding insulation may have melted and caused a minor/major internal short. You might have been luck to power it off before any damage was caused.
Isolate everything off the transformer outputs and verify the output voltages are still within spec. Set your multimeter to AC voltage when doing this - voltages are listed in the schematics on the rectifier board page and the transformer lugs are numbered accordingly. i.e. solenoid voltage is at transformer lugs 2 and 6 and should measure 49VAC across the two lugs. Note, you are measuring AC across lugs, not to ground.

Good luck!

So it was the display connector that went on the wrong way around?
Which fuses blew?
Does the LED on the MPU board come on at all during powerup?

Have you since measured voltages on the rectifier board and the solenoid driver board?