Many katas are this way, they only require pretty much some further mathematical research.

Solved it, but it's still dumb. You either see/find the magic formula or you're screwed. No programming or algorithm challenge here.

First, there is a typo in the desription. "All numbers in will be positive integers.". I guess the word "arr" is missing in there.
Second, the description create unnecessary confusion. At the beginning a range of numbers are compared to each other. But afterwards a list of number shall only be compared to one number (=n).

This kata is "Google the formula" instead of "Show your programming skill"...

Several results make no sense. Like "act(0, 6, 0, 1)": How can you throw zero dices one time? That is physically impossible. You can only reach zero points by not throwing the dices at all, no matter how many you have.
Or "act(1, 6, 0, 1)": How can you throw one dice with side values of 1-6 and reach zero points? The minimum you can reach with one throw is 1.
Or "act(0, 6, 1, 0)": You have no dice, but you reach a score of 1 by throwing them zero times? How is that supposed to work?
Or "act(1, 6, 7, 0)": You can score a maximum of 6 points with a throw, but with zero throws you can score 7 points...?
My opinion: A target of zero can only be achived with zero throws, no matter how many dices and sides you have. If the target is >0, then there should be >0 dices, otherweise return -1 or "Error". A target larger than the maximum points you can achieve should either be removed or also lead to -1 or "Error".

The desription is not correct. The description says "below n" and "smaller than n", but the tests includes n.
For n=157 the expected result is [21, 157, 173]

The instructions should be improved. It should be possible to solve the Kata without guessing and trying.

That broke all solutions...

This might be worth raising as an issue with the Python version, since other languages don't seem to have the requirement at all.

The description didn't say that the output needs to be sorted.

Needs a few more test cases. Also the description was confusing.

There is a minor error in the description. The first mentioned return string is not including a period (.) in the quotation marks (""), but it is expected as result.

All my answers fail, even though they fulfill the requirements. As an example: my answer for the first test: [[-6, 1, 3], [-1, 2, 4], [1, 3, 6]]

What's wrong?

not an issue. see instructions, or the many previous comments.

this would be a good time to re-read the instructions to see what you're allowed to do with the parts to obtain the word