Transferring files to a client from a network drive not working

When we try to transfer a file from a network drive (full access, on a domain) via GoToResolve to a customer, it  doesn't send after we click download on their end. It just sits with a grey bar. We are in admin mode and have file access in GoToResolve. Happens from either the web portal or local install of GoToResolve. It did work in GoToAssist Corporate just fine but our license for that has expired so we either need this resolved or we will have to look elsewhere for support tools.