I'd never heard of the Nimbus tire so I looked into it -- it's basically a solid tire but with proprietary materials that Specialized claims mitigate the disadvantages of typical "airless tires" (Which have been around for more than a century and have always sucked. See Bicycle Tires and Tubes)

Anyway according to Specialized, the rims can take a standard clincher and tube.

My money's on pinching the tube during installation. I did that quite a few times when I was first learning about bikes before I refined my technique. Also had the surprise tube explosion more than once... that'll drive your laundry bill up LOL.