revtex4-2 class calls
\titleblock@produce when processing
\maketitle. In turn, this macro does
Later on, it does
which effectively makes the
titlepage page style the same as the
empty page style, in which the page number is not printed.
The indirection is because in this way the document class that's eventually used for the final printing can define the
titlepage style as wished for the particular journal.
You shouldn't change the default behavior if you're submitting a paper to some journal that requires
revtex4-2. They want no page number on the top page.
If you're using the class for your own purposes, add
\maketitle. But remember to remove it when submitting or the paper could even be rejected for failure to comply with the rules.