If your B1 version is below 9.1 PL10 and installed in Windows 10, then you will get below error message,
“There is a problem with the server’s security certificate. The security certificate is not from a trusted certifying authority. SAP Business One is unable to connect to the server”
1. Upgrade to 9.1 PL 10 and above. For more information, please refer SAP Business One support platform matrix
2. Uninstall security updates KB3163017 and / or KB3163018 through Control Panel–>Program & Features–>View installed updates. Find those security certificate and uninstall it. After installation, restart your computer.
If we reinstall security certificate again, still we will face same error message.
For more information, please refer SAP note 2331786 – Older SAP Business One clients are suddenly unable to connect to server