[rich b]

From what you described; the power from the flasher isn't getting to the switch or there is a problem inside the switch.

I would remove it from the column, take it apart, and check the wire as close to the switch as you can get.

I've found internally broken wires, loose solder joints at the switch, internal corrosion, and broken internal parts.

I don't know this actual switch or it's age; but on many older ones the switches can be opened by unbending the tabs and being careful of springs, balls, and contact plates be cleaned up and rejuvenated.