Which ramp flashers flash? The entry ones? Or does it do the strobing like you made the ramp?

Does it do it in test mode as well? Likely something is shorted to the switch matrix or a jumper wire has fallen off one of the solenoids. (Or something in the switch matrix)

Inspect all the connection points by tugging on each connection to make sure they are all secure - sometimes there's something hanging by a single strand of wire so you think it's ok, but it's not.

Are they normal flasher bulbs or LED? The flashers if LED might be a red herring.

What's the voltage measurement on the flippers? Should be between 50-75 volts.

I wonder if you lost 1/2 of a bridge on the power supply.

Try reseating the transformer connectors a couple times down in the cabinet sometimes they get corrosion on the pins.

Put it on the one that says V with the solid line under it

Leave your leads where they are

Put the red lead on a coil lug

Put the black lead on the ground braid in the cabinet