GriefPrevention is powered by permissions. Every action done in a world is checked against a specific flag permission. If you are trying to figure out what is causing an action to be blocked or not to be blocked then /gpdebug is what you will need to use.

To record all flag permission checks, enter

/gpdebug record

To record all flag permission checks for a specific user, enter

/gpdebug record username

When done performing actions to record, enter

/gpdebug paste

This will generate a link which you simply double click to see output.

An example of output shown is

https://gist.github.com/anonymous/929ceebb253f12b4dc9f238e940ffe76