The game will not reset or start, or stays in a reset cycle.

Game never resets: bent coin door switch

Cause: A fragile coin door switch has been bent closed, usually by someone trying to add credits by hand, or a coin is jammed.

Checks

• Inspect and adjust the coin switches.
• Clear jammed coins and undo odd coin door modifications.

Fix

• Set the game to free play so coin switches are not needed.

Systems

• Electro-mechanical

Related tips

• Bally EM won't start: dirty game over relay contacts
• Outline of a Gottlieb reset-bank game start
• Gottlieb start halts after reels reset: S Armature switch
• Using the start sequence to find where a reset stops
• Start sequence of 1972-78 Gottlieb single players without a reset bank
• Gottlieb reset-bank game won't start
• Williams EM start-up sequence
• Bally mid-1970s EM start-up sequence

Source: Repairing Electro-Mechanical (EM) Coin Operated Games to 1978, Part One, Clay Harrell (pinrepair.com)