Your headerinclude template is empty. You need to revert it back to its original state.
ACP > Templates & Style > Templates > *Template Set* > Ungrouped Templates
Next to headinclude click on "Options" then "Revert to Original"
I don't see 'Ungrouped Templates'.
It's the last one on the list under "XMLHTTP Templates".
I don't see that either. "There are currently no global templates".
You've selected the wrong template set. "Global Templates" is for templates shared between themes.
From the looks of it, your template set should be called "Kross Templates" or similar.
I did check that one to.
Footer Templates
Forum Bit Templates
Forum Display Templates
Index Page Templates
Navigation Templates
Post Bit Templates
Is all I saw.