Harmonic dampeners - also called balancers - have an internal hub, a rubber ring and an outside hub.
The rubber ring is vulcanized to the inner and outer hubs.

When the rubber ring deteriorates the outer hub can slip and factory TDC is lost.

Try another dampener or find true TDC and go from there.

You don't need a degree wheel to find true TDC.
It can be done with a piston stop and a tape measure.

Just don't crank the starter with the piston stop in place or you'll be hearing many expensive noises.