First thing: unistall the game because you can't downgrade the version of the app, second: go to this link
Harry Potter Hogwarts Mystery Ver. 5.4.0 MOD Menu APK | No Energy, Gem & Coin Costs, Unlock Shop | - Platinmods.com - Android & iOS MODs, Mobile Games & Apps download and install the 5.5.2 version, third: start the game, at the the character creation screen log into your profile and load your save then the game will restart and ask you to upgrade. fourth: close the game, app center or play store and at this point install the 5.4.0 from platinum, then restart the game and you're finished.
let me know if you managed to do it.