Renable is not a valid word, Re-enable (or Reenable to some extent) is.

I haven't changed the kata since I first published it, so maybe they just didn't hit Submit

t3l3f00n is the other one. Maybe he didnt press submit or its a mistake from codewars.
Also if you changed some stuff in the tests, its possible that his solution got invalidated and is hidden by default.

The Codewars website says that this kata has been solved twice, but I can only see my own solution. Who's the other person?

It was automatically put in draft because it received two issues. If you resolve both, you can republish.

This kata was 'Beta', but now it is 'Draft'. Does this mean that it's no longer published and no longer available to the public? If so, how did this happen?

Issues: The prototype of the initial solution is too 'indicative'(uppercase, lowercase,...), and the std::functional in the header gives part of the solution.

Important note: you may have a templated callback there and get the possibility of using a lambda instead of a std:::functional => do not 'extern blabla' declare the solution.
See my solution: the template <typename CallBackType> void function(CallBackType callback) is the canonic way to do it.

Please tell me specifically what's wrong with the test program I wrote.
If the solution fails, it tells you specifically which input string it failed on, I think that's a decent test program.

Please use the testing framework properly. You should read the kata authoring guide to learn how to create katas

Can someone please enable C++ as a programming language?