Changed my water temp sending unit and still nothing on the gauge.

If you grounded the sender wire and the gauge pegged, then that part "may" be OK. Is it possible you overtightened the sender and damaged it? Otherwise your sender is defective

"New" does not mean "functional."

ALSO it may be that the sender molded connector has an intermittent break internally

Get a screw the same size as the sender stud, I don't remember, no6 or no8 machine screw. Put that in the sender connector and clip your meter in with the key OFF. Put the meter on ohms and shake and wiggle the connector, looking for a change in the meter reading