Well Im having the same problem as Stev, my s pen works on the bottom touchscreen buttons but not on the screen, im able to use the screen with my fingers tho.
I've been reading and I've found that the problem could be the S pen sensor screen which is behind the main screen, theres some video on youtube about how to replace it but seems to be like there's no guide here about how to do it in detailed steps.
Hope this helps, if anybody else knows anything else or somebody tried/solved it already, Please ill be grat to know.