The flipper relay clicks and there's about 37 V at the supply, but the flippers don't work in a game or in test.

Flippers dead after long storage: corroded button and EOS contacts

Cause: After years out of use, the cabinet flipper switches and the EOS switches were coated in white corrosion.

Checks

• Inspect the cabinet button switches and the EOS contacts for white or dull deposits.
• To rule out the relay, jumper the flipper ground return as the schematic shows.

Fix

• File and clean the contacts, then re-adjust the gaps.

Systems

• Williams System 6 / 6A

Games

• Tri Zone

Related tips

• Three flipper mechanism generations
• Flipper relay does not click on in test
• Flippers dead, or still live after game over: the flipper relay
• Most flipper faults are EOS switch faults
• Flipper sticks in the up position
• Games with an upper flipper switch on the EOS stack
• Flippers dead: fuse and coil voltage
• EOS switch must be normally closed with tungsten contacts

Source: Pinball Repair help group!! (Facebook group)