If you see blank puzzles/black pieces or if you can't open the app at all after transferring to another IOS device, downloading from the cloud or after the app's/IOS update, please follow the instruction:
Please reinstall the app: delete it and download from the App Store again.
If you are registered (!), your coins, levels and packs will be saved. Started, downloaded from the Feed and created puzzles will be lost.
After reinstallation please log in under your account and restore the packs.
To restore Gold Pack/All inclusive you should click on the Restore All Paid Downloads button and reboot your device (this is an important step).
Also in My Packs section you may restore the purchased puzzle packs one by one:
If you use the same Apple ID you may repurchase the packs for FREE.