To clear things up
Could you provide some background so anybody could find the problem way easier?
how did you install it? Wordpress.org or via software installation on hosting/or managed WP
Do you have SSL? If so, do you have cloudflare?
did you change to https via WP settings? Via DB? via plugin or cloudflare etc.
there might be some caching involved as well over 5 years and still having issues with specific hosting providers
also make sure everything is rewriten to https on the database
if you have dashboard access (I assume you do, it just showing you an insecure connection message), find a plugin like ‘better search replace’ and search for ‘http://’ and in the replace placeholder input ‘https://‘ and cache (in case you’re using cloudflare make sure you enable “developer mode”
also check on multiple browsers and incognito mode
don’t act on impulses first let us know more information and don’t make any database chang