Thit is exactly as I have it and it works fine:
*EDIT: Sorry I can't get the image uploaded now and need to leave, sorry!
I think the issue is you haven't saved your data as an array in the first place. You would need to save your array as json, upload it, then when you download it again it will work.
But if you want to add your values into an array, just do something like:
Repeat tokencoun(ajax.lastdata,"(chosen token"))
Set value of array at index: loopindex to tokenat(ajax.lastdata,loopindex,token)
That should work fine, but I am still very new at this!