Symptoms
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The domain "example.com" hosted in Plesk is not accessible with the following error shown on a web browser:
Error 526 Invalid SSL certificate
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While accessing using the URL "www.example.com" instead, the website works correctly.
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The website "www.example.com" is using Cloudflare, while "example.com" is resolving to Plesk IP address directly:
# dig +short example.com @8.8.8.8
203.0.113.2# dig +short www.example.com @8.8.8.8
www.example.com.cdn.cloudflare.com.
198.51.100.2 -
Unable to issue Let's Encrypt certificate for "example.com":
Error: Could not issue a Let's Encrypt SSL/TLS certificate for example.com.
The authorization token is not available at http://example.com/.well-known/acme-challenge/_sJGmwn5GZYcXm8nqwAMKLBvOpBXLaokwCHjby3MvY4.
To resolve the issue, make sure that the token file can be downloaded via the above URL.
Cause
There is a Cloudflare misconfiguration.
Resolution
- Change the SSL configuration on Cloudflare to "Full" as recommended on this CloudFlare guide, or contact the Cloudflare Support team for further investigation about the source of this error.