Unable to make any in-game purchase

From 17th Oct, I am no longer able to make in-game purchases that need real $. I can still see these packs in the store, but their prices are shown as "Tap for Price", and after I click it, a notification of "Please ensure you have network connectivity and a valid billing account. You have not been charged" pops out. The issue cannot be fixed by going into settings and restoring purchases which worked once before when I had a similar issue. Later when I checked the online web store via my phone, those packs that require $ to be charged are not there, so as the crystals (vaults).

This has never happened to me before. And with all settings unchanged throughout the last 5 yrs, it baffles me. I've tried to switch off/on my phone, re-login my APP Store & Game Centre, and re-install the game itself, they all failed.

Any info or suggestion to make it work would be greatly appreciated.