If you havent tried doing so, enter the pws name without “pws.”
The firmware will convert your location to latitude, and longitude. So if all else fails, go to WU, navigate until you are showing the weather using your pws. Then look at the location there, it will show the lat and long coordinates. Enter those as your location, and as long as your pws is up and running it will use it. If for some reason your station goes offline, it will use the nearest available.
Another thing to take in to consideration, some of the weather data is cached and averaged, the averaging process may not use weighting for the data, which could skew the final result a small amount. Weather is read every hour and the cached data is reset at midnight. If you continue to have no luck, you could look at the api documents and enter your location manually.
I hope that helps a bit,