car won't crank or read codes after repair of harmonic balancer. on 2006 Ford Explorer

also changed crankshaft position sensor and belt,now engine won't crank,battery very low tried to jump.

1 answer
WAS IT RUNNING OK BEFOR? DID BALANCER CUT HARNESS TO CRANK SENSOR DUE TO SEPARATION AND CAUSE ENGINE TO STALL?
REPAIR= REPLACE? BATTERY NEED TO BE REPLACED? WE NEED MORE DETAILS!