An unexpected block usually comes from a category that includes more apps than you meant to select.
Check categories first. Open the Blocks tab, edit the list, and switch from a broad category to individual apps if you want more control.
Check Always Blocked. Apps there do not open for coins or a Scroll Pass.
Check for a Lock In session. During Lock In, the selected apps stay blocked even when you have coins available.
To remove an app, edit the list and deselect it. If the app has disappeared from your Home Screen instead of showing Aura's shield, read iOS says an app is restricted.