I had the same issue with QR codes not being scanned. After installing sandboxed Google Play, the issue disappears. Network Access for at least one of the 3 Google Play apps is required. My test was with Network Access disabled first for all 3. When that didn't work, I enabled access for all three, and it started working.
I was hoping to avoid Google Play all together, but it looks like I found my first reason to start using User Profiles.