This is a fantastic question! And welcome to RStudio Community! If I recall correctly, this type of error generally means "something that Connect did not expect." Are you seeing this often? If you open up your browser devtools, the Console tab should have more information (or failing that, the Networking tab).
Depending on what the error is, it may be only client side and not have any errors on the server.
If you can let us know what the devtools look like, we may be able to give some more guidance!