How to send second invite to someone after declining first one?

[isaac1222]

I sent an invite to join the deadlock playtest to a friend of mine a while ago but they declined the invite. Now, after the latest update they want to get in. However, apparently since they declined the first invitation they are not allowed to receive another one? Is there a way to fix this? Does someone else just need to send them an invite and that'll work? Any help would be appreciated!