I think the demos (and any "Run the simulation") buttons are likely to be broken for good (they rely on outdated Java that most modern browsers won't run). We try to steer students around them but a better long-term solution will be to host that book on our servers and cut out the demos entirely.
In the immediate term, if you have an iOS device, this iBooks version might be useful:
And PDFs can be frustrating to read for any length, but this version helps to ignore the demos or any other broken bits:
For the Direct Credit final exam, you won't use the binomial calculator, but will be able to use a scientific calculator and statistical tables, namely these: