If you’re sure all the wiring is good I’d start with the alternator. Its possible you got a bad unit out of the box.
If you have a voltmeter handy, try the following: Connect the negative lead of the meter to the positive lead of the battery. Then connect the positive lead of the meter to the B+ terminal of the alternator. With the engine running it should read less then 1 volt. If its over 1 volt you have a connection problem.