the default "pagename" is not valid on "custom links" (even if you send it, it will be deleted/ignored).
in most cases people are either having a "prop" with the page URL or using an eVar for the pageName (just dublicate the default "pageName"). thanks to expiry the eVar is still valid on the next call so you can breakdown by the eVar.
if you don't have the data yet (custom prop or eVar), try to create a segment with the desired hits and run a warehouse report with breakdown by the default "pageURL" (never tried if that works on custom calls, but worth a try)