Problem rendering part of demo page

[AzzieDev]

http://mathb.in/1

At the bottom, for

When this is combined with \eqref{summation} we obtain \eqref{theorem}.

it returns

When this is combined with (???) we obtain (???).

My suspicion is something changed with MathJax and it was updated on the main site, but this line was overlooked or forgotten about or was like that, to begin with.