As far as I know, there is not one platform that both parties have agreed to be on. Without that, it is very difficult because of what we have seen. For example, MSF and even UN agencies have tried engaging bilaterally with each of the parties to unblock the humanitarian access problem. The problem is that whatever one party has agreed to offer to improve the situation, the other party does something to sabotage and cancel it.
Indeed, some kind of platform is needed to bring the parties together to unblock the situation.