Re-establishing permission inheritance between spaces
You can re-establish inheritance of permissions between parent spaces and their child spaces if the inheritance has been broken previously by customizing the child space permissions.
Fastpath:
Note that by re-establishing inheritance you remove any customizations you've made to permissions in the sub-space and in spaces that inherit from the sub-space.
To re-establish permission inheritance between a parent space and its child space:
The inheritance from the parent place is re-established, all permission customizations of the child space are removed, and the permissions from the parent place are applied to the space.