I had opened my mailbox and noticed that in addition to the Explorer's returns, there was a mail with my converted returns from the last event (coins), and a gift which I could see included 10 building permits (yay!) and something else that I now can't recall. So, happily, I ticked to collect everything.
Immediately, I got an error message:
https://ibb.co/BN9bmXQ
It wouldn't let me copy the error message, nor could I scroll through it. So because the screen had frozen (the ever-present, ever-annoying Zone Refresh, I guess), I refreshed the screen.
No extra building permits appeared, so I logged off and on again.
There are still no extra building permits, and as far as I can see, I also don't have any of the other items that I collected from the mails.