You could be having a curl time out during the import. We would highly to suggest that you use a child theme. This allows you to make code changes that won’t be overwritten when an X update is released.
After the child theme is set up, please add the following code in your child theme’s functions.php file
//adjustments to wp-includes/http.php timeout values to workaround slow server responses
add_filter('http_request_args', 'bal_http_request_args', 100, 1);
function bal_http_request_args($r) //called on line 237
$r['timeout'] = 15;
add_action('http_api_curl', 'bal_http_api_curl', 100, 1);
function bal_http_api_curl($handle) //called on line 1315
curl_setopt( $handle, CURLOPT_CONNECTTIMEOUT, 15 );
curl_setopt( $handle, CURLOPT_TIMEOUT, 15 );
Tip: After your child theme is setup, please review how we recommend making template changes in Customization Best Practices._
Please let us know how it goes.