First of all, you should test pings between you and your assistant. If pings works on hamachi well, then maybe something blocking the windows server like firewall? Check firewall exceptions 
Invisible is good feature for admins, spectators etc. But if u want to make player invisible just for action like a change visual, u should use unspawn instead of invisible.
Invisible is good feature for admins, spectators etc. But if u want to make player invisible just for action like a change visual, u should use unspawn instead of invisible.