Foot starter button will not turn motor over

[TMH1953]

1931 model a with 6 volt system. I'am new to model A's . The car has been starting great up until today. Started car and backed it out of garage and turned off ignition switch. Later got ready to for a drive turned ignition switch on hit pushed foot starter button and nothing happened. Ch checked voltage at starter motor 6.6. Volts. Checked voltage at coil 6.6 volts. Put car in 3rd gear and rocked back and forth about 2 foot forward and 2 foot backward while watching fan fan was moving back and forth. What could possibly be wrong.