From 2002, I have seen various international players expressing their interests in getting involved in resolving the Kashmir dispute.
Here is a list:
I hope you are able to see a pattern here which is India rejecting mediation offers every single time when someone steps in.
But, can you guess why?
Well, the answer is, India has nothing to gain from the mediation, only has a lot to lose. The mediation will result in India giving some kind concession to Pakistan in terms of either land-sharing or something more serious like holding a plebiscite in the area. That is why India is much scared about mediation.
India's prevailing strategy seems to be keeping Pakistan financially weak by spreading propaganda so that they can't get foreign investments (especially from the West) and thereby can't become an important economic player and to able to spend more in the area of defense. In the meantime, India can bring some demographic modification in Kashmir so that Kashmiris can't continue their protest/struggle: