I would check to see if your Nissan OEM portable charger unit (EVSE) works by plugging it into at a NEMA 14-50 receptacle and try charging from it. If it works fine, then the problem may be with that Westinghouse adapter you purchased.
Amazon indicates that this Westinghouse adapter is often returned (see bottom-right corner of the pic below), so you may want to return it and buy a different adapter. I do not have any experience using
6-50P to 14-50R adapters, so I can't recommend one to buy.
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