If you receive any error messages before verifying, please check the below tools for more information:
Check for User-Agent filter
During HTTP verification the file needs to be readable for our automated ZeroSSL systems. Some webservers can prevent that and only allow human interaction with a web-browser.
✅
When you get 200 OK
everthing is okay.

❌
It looks like your server has some kind of filter/firewall enabled.

👉 Check if your website is reachable for ZeroSSL
curl domain.com/.well-known/pki-validation/
ABCDEFGHIJKLMNOPQRSTUVWXYZ123456.txt
Check for HTTP redirects
During HTTP verification the file needs to be available via HTTP 200
code. Any kind redirect can influence the verification result.
✅
When you get 200 OK
everthing is okay.

❌
Any redirect with 3XX
can prevent verification of your certificate
❌
The403 Forbidden
status indicates that the server understood the request but refuses to authorize it. Please check your internal server configuration
👉 Check if your website is reachable via HTTP 200
curl -vv domain.com/.well-known/pki-validation/
ABCDEFGHIJKLMNOPQRSTUVWXYZ123456.txt