[Troubleshoot] Real-time collaboration on HTML Canvas

I've a website which allows users to post image on the canvas. Currently, we are using TogetherJS (we are open to other solutions as well) to enable collaborations between the users on the canvas. However, the users cannot see other members on the canvas but cannot see the updates made by other members on the canvas at all. We are looking for developers who can help us resolve the issues in order to enable our users to collaborate and add elements on the canvas in real-time. Please PM for more detail.