For all of you having an installation issue with RTB4, I have solved it.
When you have DL'd your RTB4, it might be named:
System_ReturnToBlockland(1)
It has the (1) After it if you have the old v3, which is still named
System_ReturnToBlockland
How to fix it:
Rename the RTB4 and get rid of the (1) at the end. This will make it so that it can be found correctly.
Then, go to
(Username)>Documents>Blockland
DO NOT OPEN THE ADD-ONS FOLDER.Drag your RTB4 into your Add-Ons folder, but remember,
Do not open it.That should be it.