Had the same issue when I set up family purchase sharing and accidentally hide Minecraft from my kids and couldn't unhide. It just lets you click on the app but freezes.
In order to fix the issue I downloaded iTunes onto my old Windows Laptop (as no option on my MacBook) and followed these steps:
Store> Scrolled down to the bottom and clicked Account under Manage>Logged in> Scrolled down to iTunes in the Cloud and clicked on Manage next to Hidden Purchases> Apps>Found Minecraft>Unhide
Worked a treat, sorry if the steps are a bit clunky but hope this helps anyone having the same issues.
It appears there's a bug with the unhide, as if it's unhiding through these steps but no options on the iOS/MacOS.