[Microsoft SQL docs]: Error 40615 'Cannot open server' means the client IP is not allowed by the server firewall: configure firewall settings on SQL Database through the Azure portal. Error 5 with 'Cannot connect' means port 1433 is closed for outbound connections on a firewall between the client and the internet: open it. If login failures (18456, 40532, 40615) hit only specific client networks, suspect a hosts file or static CNAME pinning the server FQDN to a retired gateway IP: remove the override, flush DNS, and re-test.

Context: 40615 always means the firewall blocked the client. Fix the rule, not the connection string.