NET::ERR_CERT_AUTHORITY_INVALID when accessing firewall on MAC

When trying to access one of our firewalls on the web console using a MAC we got the above error.

We have removed the certificate and Sophos Endpoint protection which did solve the issue. We then reinstalled SEP without any issues,  however the above error has now returned. even proceeding to the unsecure page of the web console gave us the same error. please see below for full error details.

NET::ERR_CERT_AUTHORITY_INVALID
Subject: Appliance_Certificate_tgmmz9zQFisPT2m
Issuer: Sophos Endpoint RSA Root 1
Expires on: 31 Dec 2036
Current date: 22 Jul 2024