No longer able to update existing prototype link

I am unable to update the developer link for my prototype – the only option I have is to create a new link. I am still using the same document and same screen as my home screen. I had saved a copy of the document (which is on a local drive) to the cloud, so I suspect this is when the problem occurred.

It's pretty devastating as the original link contains hundreds of comments by both myself and development, so we can't just jump ship and start over with a new link.

This is a critical issue at this point in our project so I'd be happy to receive any pointers as to how I might resolve the problem and update the original link.