I wrote another function that is supposed to just print the passed string via cout and I also get the subroutine not found error
It's hard to be certain without seeing the code, but it sounds like Inline might be unable to bind to the function.
Rather than having anything to do with the arguments being passed, this would more likely be due to an unrecognised type being returned by the function.
We really need to see the code you've tried, along with the error messages you're getting in order to be of much assistance.