gmail SMTP Test Error

There was a problem while sending a test email. Related debugging output is shown below:

Versions:
WordPress: 4.9.4
WordPress MS: No
PHP: 7.2.2
WP Mail SMTP: 1.2.5

Params:
Mailer: gmail
Constants: No
Client ID/Secret: Yes
Auth Code: No
Access Token: No

Server:
OpenSSL: Yes
PHP.allow_url_fopen: Yes
PHP.stream_socket_client(): Yes
PHP.fsockopen(): Yes
PHP.curl_version(): Yes

Debug:
Error while sending via Gmail mailer: cURL error 7: Failed to connect to www.googleapis.com port 443: Connection refused (see http://curl.haxx.se/libcurl/c/libcurl-errors.html)