Same thing happened on the same site when UND webcasts were first offered for purchase. The sample video never buffers and starts, just says "connecting". It was a site glitch, and the sample video later worked. Looks like it's back to not working again.
Just checked the signup from the Sioux site:
https://www.nmnathletics.com//flexReg/doReg...DB_OEM_ID=13500
and the same sample video no longer works there either.