cURL error 7 occurs when the PHP cURL extension cannot establish a TCP connection to the target host. The error is raised before any HTTP data is exchanged, so WordPress reports a failure to reach the remote server.
Typical triggers include outbound network blocks, DNS lookup problems, SSL verification failures, or mismatched cURL/OpenSSL libraries. When the connection attempt is refused or times out, cURL returns code 7 and WordPress surfaces the message in admin screens.