When saving an IPC or HR Activity you receive the following error, despite filling in all mandatory fields:
This occurs because there is a hidden mandatory attribute on the window that has no label.
You are most likely to see this behaviour in the HR domain when trying to create an HR Activity because the visible Title and Description attributes on the window are actually from the Activity object. The Process object's Title attribute is present on the window, but is hidden and has had its label removed. This is why you get an empty space in the error box where the label name ought to be.
Create a template to populate the hidden field, or make the field visible, if appropriate.
The OOTB database provides templates for each of the HR processes which set the Title to ".". When using the OOTB windows you must set the template on the shortcut so the Title gets populated.
The HR window is arranged in this way to keep HR data secure. Not everyone would have access to the "Activity" object, but everyone has access to the Process Object, so anyone who can write a query on the Process object would otherwise have access to sensitive HR data. In this configuration, the only results they would receive are Titles of "."