We can check out what is failing and why and when. Excel connector is in essence a web browser connection, so If it is a connection timeout, that can have many causes. But I can’t be specific 'til we’ve tested it out.
We’ve just made some improvements to the amount of data that can be sent from the excel connector. Could you try it now to see if it works?
note: the send operation may take a bit of time and the UI doesn’t (yet) give good feedback that a send operation is going on. It took me about 40s to send the entire document that you sent