I migrated a website of 500,000 URLs from HTTP to HTTPS in 2017 (through a 301 redirection via htaccess). Today I've been checking the 'Coverage' section of the old HTTP property (within 'Google Search Console), and found 100,000 URLs with the error type "Duplicate without user-selected canonical".
The 'last crawled' date of all of these URLs are prior to November 2019 and most of them are from 2017. I wondered why this is happening.
- all the URLs work ok
- all the URLs are showing a valid canonical URL (with the HTTPS)
Any shared similar experience would be welcome. Thank you.