It works perfectly like what I need!

As said in other review, it's impossible to enter manually a code since they got saved in lower case while the are entered in upper case... The fix: Modify the plugin -> locate function create_invitation_code in back-end.php and replace $code=... by $code = strtoupper(sanitize_key( $code )); Now the code you create are correctly saved in upper case but there I already saw other bugs (code deletion not working well)

put in code and all i get when i try to register is - ERROR: Wrong Invitation Code. - i'm copying and pasting so i'm putting the wrong one in!

Why can i only make 10 codes at once? i need at least 400... Thanks!

very helpful plugin.This is real beauty of FLOSS (Free & Libre Open Source Software)that you get funcionality that is very helpful that too is with source code.& if you are happy with it you may go for Pro Version (if developer is offering) or may enhance by yourself or can hire somebody. Thanks bro for this very useful & helpful plugin. One suggestion for system generated code : one more text field not to use certain confusing characters by admin.He will type some chraracter so it will not generate those characters set in code. Note : 1.I have not checked that whether email is delivered to registered or not since this is tested on localhost. 2. One minor problem in manual code functionality.It creates code automatically in LOWER CASE & on registration it creates automatically in UPPER CASE.So it is immpposible for users to register those user who have manual code.

Doesn't work, poor documentation, missing textdomains, etc...