Fatal error granting permission

When Granting permission to the site withing Gmail, I get the following error when I press Allow

Fatal error: Uncaught GuzzleHttp\Exception\RequestException: cURL error 60: SSL certificate problem: unable to get local issuer certificate (see http://curl.haxx.se/libcurl/c/libcurl-errors.html) in C:\inetpub\wwwroot\Cypriotsworldwide.com\wp-content\plugins\gmail-smtp\google-api-php-client\vendor\guzzlehttp\guzzle\src\Handler\CurlFactory.php:187 Stack trace: #0 C:\inetpub\wwwroot\Cypriotsworldwide.com\wp-content\plugins\gmail-smtp\google-api-php-client\vendor\guzzlehttp\guzzle\src\Handler\CurlFactory.php(150): GuzzleHttp\Handler\CurlFactory::createRejection(Object(GuzzleHttp\Handler\EasyHandle), Array) #1 C:\inetpub\wwwroot\Cypriotsworldwide.com\wp-content\plugins\gmail-smtp\google-api-php-client\vendor\guzzlehttp\guzzle\src\Handler\CurlFactory.php(103): GuzzleHttp\Handler\CurlFactory::finishError(Object(GuzzleHttp\Handler\CurlHandler), Object(GuzzleHttp\Handler\EasyHandle), Object(GuzzleHttp\Handler\CurlFactory)) #2 C:\inetpub\wwwroot\Cypriotsworldwide.com\wp-content\plugins\gmail-smtp\google-api-php-client\vendor\guzzl in C:\inetpub\wwwroot\Cypriotsworldwide.com\wp-content\plugins\gmail-smtp\google-api-php-client\vendor\guzzlehttp\guzzle\src\Handler\CurlFactory.php on line 187
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Regards
Pete