Your connection is not secure
The owner of www.pi-hole.net has configured their website improperly. To protect your information from being stolen, Firefox has not connected to this website.
Learn more…
Report errors like this to help Mozilla identify and block malicious sites
www.pi-hole.net uses an invalid security certificate.
The certificate is only valid for pi-hole.net.
Error code: SSL_ERROR_BAD_CERT_DOMAIN
Make sure the date and time on your computer are current.
This can cause security certificates to appear invalid.
That’s one possibility, anyways.
I am using Firefox, latest version, on MacOS High Sierra 10.13.6 and I don’t get that error when I visit pi-hole.net