Mathcad Not Returning Function

Actually your sheet is to confusing for me so I can just note what I noticed.

At first you have to realize that writing B]x does not create a matrix even though it may (unfortunately) look that way in Prime.

The vector in your sheet is simply S

But

still throws an error and if you use Prime's error tracing you arrive at

The next position is

So I suggest you follow the error chain and manually evaluate the functions using the very same argument(s) you use in the offending function call. That way you may see which functions returns a data structure which is not compatible with the function you defined.

The reason for the root function failing may be the R.palmer function, because this function does not return a scalar but a 2x1 vector

Not sure if the R.palmer function is supposed to return that vector.

Using just the first element of this 2x1 vector makes at least the root function work