Support
I bought the unlock on another iPhone
Settings → Restore purchases, signed in with the same Apple ID you bought it with. It is a one-time purchase, so it is yours on every device that Apple ID uses, forever.
A shared link opens Safari instead of the app
Tap the link from Messages, Mail or Notes rather than pasting it into Safari. If that still opens Safari, the app itself may not be installed yet - the link plays the board in the browser either way.
My progress disappeared
Progress lives on the device, so deleting the app (or resetting progress in Settings) removes it. Reinstalling starts the campaign again; a purchase, unlike progress, restores from Apple.
How do I get a refund?
Refunds are handled by Apple, not by the game: visit reportaproblem.apple.com. If a refund is granted, the unlock is removed from the app automatically.
The game is silent
Settings → Sound, and check the volume. DoggoDoku plays through the silent switch on purpose, so the game's own Sound setting is the one that decides.