I do confirm that running both of 16.0.15330.20264 Or 16.0.15601.20148 have the same problem of tying to connect message
not only in excel but related in outlook too (when you try add attachment)
current setup we use is with roaming profile(folder redirection user)
rolling back to 16.0.15225.20288 fixed the problem
While the message "trying to connect" is displayed, we can observe the computer trying to connect to each Domain Controller of our domain oh HTTP port 80 !!!! too validated from client firewall log. please share if fix is already done