My book of natural aura got reset after a crash and it doesn't unlock anymore. Is there any way to force unlock things?

You can unlock the entire book for your current player using the command /advancement grant @p from naturesaura:root. You can also go into the Patchouli config file and disable advancement progression altogether.

Could you report this issue to the Patchouli repository and maybe cross-reference this issue as well? I'm not sure this is something for Nature's Aura to fix. Thanks!!