However the MWE here introduces an unwanted blank page from the call to \setuppagenumbering[state=start].
And the \setuppagenumbering has to come after the \page, of course.
yours sincerely
dr. Hans van der Meer
% test pagenumbering start-stop
\setuppapersize[A5][A5]
\starttext
\setuppagenumbering[state=stop]
\ConTeXt\space\contextversion\blank
This is page 1 without pagenumber.\crlf
\page
\setuppagenumbering[state=start]
This should be a page with pagenumber 2.\crlf
But the pagenumber is 3 instead after blank page 2.
\stoptext