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Unable to install Let's Encrypt SSL Certificate for domain
ERR [panel] Let's Encrypt SSL certificate installation failed: Challenge marked as invalid. Details: Invalid response from http://example.com/... [127.0.0.1]: 503
Document root folder of the website contains file "app_offline.htm".
The purpose of "app_offline.htm" is to disable any other pages from being requested.
To install certificates temporarily rename file "app_offline.htm", after successful installation rename it back.
If you want a permanent redirect from HTTP to HTTPS, please, go to Subscriptions > example.com > Hosting Settings and select "Permanent SEO-safe 301 redirect from HTTP to HTTPS" .