You must accept the inv to join a PL.
I got tons of invites every month and I decline them all. I just don't want to play a PL at the moment, and that's all, I have lot of other stuff that I'm focused on BB so I would like a button where I'm not able to be invited for a PL :)
I think that I have invited you once. I hope that there will be button to block all invites, but also once manager blocks it, that there is an info on his team hq that he has blocked it.