Invalid certificate or unknown issuer thrown behind firewall

[x1x11x]

The certificate looks good, as long as iam not behind a firewall, if i am, the browser shows me an error which says either unknown issuer or invalid cert.

I’ve checked my website with check-your-website.server-daten.de - everything seems valid

My domain is: kiseni.com

My web server is (include version): IIS 10

The operating system my web server runs on is (include version): Windows Server 2016 Datacenter

My hosting provider, if applicable, is: Contabo

I can login to a root shell on my machine (yes or no, or I don’t know): yes

I’m using a control panel to manage my site (no, or provide the name and version of the control panel): Plesk Onyx

[JuergenAuer]

Hi @x1x11x

@x1x11x

My domain is: kiseni.com

there is an older check of your domain. Your certificate is new

CN=kiseni.com
	10.04.2019
	09.07.2019
expires in 88 days	*.kiseni.com, kiseni.com - 2 entries

the main domain and every subdomain is secure. No chain error, no mixed content. So I don't see a problem.

So:

@x1x11x

The certificate looks good, as long as iam not behind a firewall, if i am, the browser shows me an error which says either unknown issuer or invalid cert.

Share a screenshot.

PS: *.kiseni.com doesn't work with a sub-subdomain like www.blog.kiseni.com.

[x1x11x]

Hi!

I’m not at work currently, but i can show you the message:

Regards!

[JuergenAuer]

Looks like there is a Man in the middle.

A firewall or anti virus software that creates an own certificate to read the encrypted traffic.

That’s a problem of that connection / firewall / anti-virus-software, not one of your website.

[x1x11x]

I’m glad to hear this.

Thank you very much @JuergenAuer