When I logged in this morning, I got a notification that there was a free pack available in the shop. I clicked the link in the notification to go straight to the free pack and accepted it, but then there was no pack to open.
I see the similar-seeming bug report/update indicating a similar issue has been resolved recently with the golden pack, but this happened only this morning.
Easy come easy go, but just FYI while I am reporting other bugs
Edit: restarting the app caused the pack to appear.