Issue in opening shared diagrams

Hey Ashwani thanks for reaching out! I’m sorry for the trouble you are having with sharing. In most cases involving issues with sharing unsharing and resharing the document resolves the problem. I would recommend trying this before you go any further. If you don't know who shared the link it should be available in your email inbox or in your account under the notification bell.

I also want to recommend checking your 'Shared with Me' folder for the document as sometimes it will be there already.