Not really with so few information. What are the differences when it works and when not?
Also you are perfectly right, speed and bandwith are not of any concern as VST Connect can deal with very low bandwidth - chek upload settings, but I doubt it can even outrun your bandwidth no matter how you set it.
What does matter is the quality of the connection, packet loss, clumpsy WiFi, phone tethering, superflous “security software/virus checkers” etc and most of all, apps running in parallel that use LAN or internet.