The current pre-release of the client ("pioneer" in the version) is only compatible to itself. So you can only play with other testers. Please be aware!
@MarredTen19 I dont know how much effort you want to put into this but what you could try is to download the windows-iso of your current system and backup from the iso. (watch out to select the option to keep all files and stuff)
Pretty sure that will fix it, but its a bit of effort