So, make sure to check your internet connection whenever you are unable to join a private server. If you are still unable to ...

Activating a private server code can ... per account on their Roblox page. If you do it in-game though, it will always require you to pay a monthly fee of 800 Robux to make and keep a server ...

Roblox, however, says it’s making private servers available for free in Party Place, so parents and kids can create a place where only those friends they directly invite can join and play.

So, make sure to check your internet connection whenever you are unable to join a private server. If you are still unable to join the private server on Roblox, we recommend contacting Roblox Support.