Needs random tests.

"Look at the test for the entire spec" is not an acceptable form of description. The description should be self-sufficient to describe the task (unless the whole point is to figure out the task, but this kata isn't one of them).

Ranking cannot be changed (anymore)

I also agree. It use to be hard for me to do a 5 kyu, or even 6 kyu, and this seemed very easy to me.

I agree. This exercise seemed much easier than other 4kyu kata.

Shouldn't be 4 kyu, more like 6.

Better regex, more logical, and more efficient than a lot of the other solutions I've seen. What do you think?

Doesn't this call lcm for each element? That doesn't sound clever.

no worries, good luck :)

Thanks matt, that's great. Much appreciated.

put simply you've returned the wrong answer, run these test cases for a more detailed and responsive version..

collection = (1..24).to_a
helper = PaginationHelper.new(collection, 10)

Test.assert_equals(helper.page_count, 3, 'page_count is returning incorrect value.')
Test.assert_equals(helper.page_item_count(1), 10, 'page_item_count is returning incorrect value.')
Test.assert_equals(helper.page_item_count(2), 4, 'page_item_count is returning incorrect value')
Test.assert_equals(helper.page_item_count(3), -1, 'page_item_count is returning incorrect value')

Test.assert_equals(helper.page_index(23), 2, 'page_index returned incorrect value')
Test.assert_equals(helper.page_index(24), -1, 'page_index returned incorrect value when provided a item_index argument that was out of range')
Test.assert_equals(helper.page_index(40), -1, 'page_index returned incorrect value when provided a item_index argument that was out of range')
Test.assert_equals(helper.page_index(3), 0, 'page_index returned incorrect value')
Test.assert_equals(helper.page_index(-1), -1, 'page_index returned incorrect value when provided a itemIndex argument that was out of range. pageIndex(-1) should return -1')
Test.assert_equals(helper.page_index(-23), -1, 'page_index returned incorrect value when provided a item_index argument that was out of range. pageIndex(-23) shoudl return -1')
Test.assert_equals(helper.page_index(-15), -1, 'page_index returned incorrect value when provided a item_index argument that was out of range.')

Test.assert_equals(helper.item_count, 24, 'item_count returned incorrect value')

helper = PaginationHelper.new([], 10)
Test.assert_equals(helper.page_index(0), -1, 'pageIndex(0) called when there was an empty collection')

you still haven't specified the error..
or your actual code you've written

When reporting an issue it is very important you post information because nothing can be done when no information is supplied.

Please post your code below and mark it as a spoiler and also add some information about the issue,

Thanks :)