Page declares more than one canonical tag

A canonical tag tells search engines which address is the "real," preferred version of a page, and a page should only ever declare one. This check flags pages that declare more than one canonical tag at once. On this site, one or more pages have this conflict. Two canonical tags give Google contradictory instructions about which URL is preferred, and it may pick one arbitrarily or ignore both, which undermines the reason for having a canonical tag in the first place. This is a common conflict caused by a CMS plugin and theme both adding their own canonical tag. Your developer should find and remove the duplicate canonical tag so exactly one remains per page, often by checking for a plugin, in WordPress commonly an SEO plugin conflicting with the theme, that is adding a second one. This is usually a quick fix, under an hour once the source of the duplicate is found.