Temp sending unit question

[72LB]

The temp gauge hasn't worked in my 69 since I recently bought it. I've tested the gauge and it's working so I changed the sender( twice so far ) and nothing. It's the spade type connection which was in it when I got it but is it possible it's the wrong sender? I told the guy at the parts store it was for a gauge but I just noticed on rockauto that the gauge sender has a button head not the spade connection. Have I been putting in the wrong sender?