Stop! This website is blocked

Hello everyone, 

Recently i noticed a bunch of tickets regarding the following.

i want to go on facebook, but facebook is blocked.

instead of the blocked page i get Error code: SEC_ERROR_UNKNOWN_ISSUER(firefox) or NET::ERR_CERT_AUTHORITY_INVALID(chrome)

it works fine if i install the sophos certificate.

I understand that the certificate must be pushed to end devices,  however i can not ask guest users to install the sophos certificate. 

I also understand that that this can be secured with a public cert.

This seems so random, as for some customers works just fine, but for others not.

I can not ask 200+ customers to buy a certificate to display a blocked page on guest networks. 

Can anyone advise?

Kind regards,


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[edited by: Erick Jan at 1:48 AM (GMT -7) on 31 Oct 2023]