Hi @Greg Booth Did you configure the TLS connection correctly? Has your certificate expired?
For configuring TLS connection on native mode report server, you can refer to this link: configure-ssl-connections-on-a-native-mode-report-server.
Also, I found a link that lists possible causes and solutions for the error "The remote certificate is invalid according to the validator warning", maybe you can check it based on the content of this link. https://www.positioniseverything.net/the-remote-certificate-is-invalid-according-to-the-validation-procedure#:~:text=The%20remote%20certificate%20is%20invalid%20according%20to%20the,the%20hostname%20you%20use%20to%20contact%20the%20server.
Best regards, Aniya