Hello,
In /admin/config/content/protected_node. In the tab Protected node email support
Email node information field do not support value under 10x2 but that is not explained in the help text and not explained in the error message.
So it needs to be fixed.
And also, I will make a checkbox to activate the feature, because I think that's not natural to fill a textfield to activate a feature.
I will upload a patch.
Fixed
1.0
User interface
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