Left flipper was dead. Voltage was good at switch. Traced problem to left lug on coil. The plastic holding it had broken off and it was only connecting when wiggled. Replaced it with a new FL-20 coil. Tests good.

One note on these is that the screws holding the stop plate have nuts behind them. If the screw is hard to turn, loosen the nuts first. That may require taking the flipper assembly off the wood.