my bad, forgot to add a space after the commas

As you could have seen in "Sample Tests" the test is:

assertEquals("[[1, 1], [42, 2500], [246, 84100]]", SumSquaredDivisors.listSquared(1, 250))

Your code is wrong somewhere.

expected:<[[1, 1],[$[42, 2500],$][246, 84100]]> but was:<[[1, 1],[[42, 2500],][246, 84100]]>

why is there a white space in the second item. the space is occuring in the position of "$" symbol

as you can see here this requires at least Kotlin 1.5, but this Kata is only available in Kotlin 1.3

IN KOTLIN
error occurs when converting char to int using "Char.digitToInt()"

Error
src/main/kotlin/solution.kt:5:29: error: unresolved reference: digitToInt
val list = num.map { it.digitToInt() }.toMutableList()
^