I got a reminder today. Probably because I never got the invite from Geekfunder in the first place. I got the Kickstarter update that the pledge manager was open, plugged my email address into the link and was told my pledge manager invite was being processed. Figured I'd receive my invite in the next few days and forgot all about it. Till I got my reminder today of course.
Other Kickstarters are pretty vocal during the pledge manager stage, reminding backers several times to complete said pledge manager. But the only communication I received for the Zombicide Invader pledge manager was one email when it opened and one email five days after it closed. I admit my inaction was partially to blame but I should not be penalised for someone else's lack of communication.
Did you try following the link today? it looks like it might still be active. Perhaps they're doing an unofficial extension to get some extra orders...