Peggy.
May ask some dumb questions.....if so, just trying to help but hard to see from pictures. Please ignore.
In your side by side pictures, the new dash has a dressing (plastic panels creating a 2 layer dash) on the right and left sides. The old dash does not appear to have this dressing. Did you move those panels from the old to the new dash? If not, can those panels be removed with a couple of pins/screws? I ask because in your first pictures it appears that the dash may be catching on something up top, keeping it from dropping in like it should. If the two dressing pieces can be easily removed, I would do so and then see if the dash fits better.
I looked at the dash between model years. 2016s (early) used a different part number, then the part was rolled to 5453137 likely with 2016.5s. That should be the part number for both your two dashes, correct?
Finally, if you take your old dash and put in back in place, does it line up as it should? The first pictures to me really look like interference, you need to get the top/front of the dash to drop down some.
Just a couple of questions......the company you ordered from does sale Polaris stock parts, and if the numbers match, would be hesitant to order a new one. It is possible one got damaged if stacked etc, but.......