indexing.redirect-chainToo many redirects before the page
Why it matters
Every redirect is another round trip before anything loads, and crawlers give up on long chains. Google's advice is to "keep the number of redirects in the chain low, ideally no more than 3 and fewer than 5"; Googlebot stops altogether after 10 hops, and link-preview scrapers are less patient than that. A loop never arrives at all, so the page can't be indexed or shared.
Sources: Site moves with URL changes for 3 and 5; How HTTP status codes affect Google's crawlers for "Google's crawlers follow up to 10 redirect hops". We warn over 3 hops and call 5 or more an error.
How to fix it
Point the first address straight at the last one. The usual cause is rules stacked over the years (http → https, then → www, then → a trailing slash, then → a renamed page). Replace them with one rule that goes to the final address in a single 301, and update your own links and sitemap to use the final address.