I am also able to typeset Aditya’s example without problem, so example file is OK for me.
There may be something which is not in the file.
I am using MKIV beta 6. 21 version under OSX.
This is LuaTeX, Version 1.05.0 (TeX Live 2017)
system commands enabled.
open source > level 1, order 1, name '/Users/graph/ConTeXt/tex/texmf-context/tex/context/base/mkiv/cont-yes.mkiv'
system >
system > ConTeXt ver: 2017.06.21 23:03 MKIV beta fmt: 2017.6.25 int: english/english
Best regards,
Dalyoung
About \setupheadertexts : simplify a code