The message of “No response from server” indicates that your server is having trouble connecting to the CrossRef server at https://api.crossref.org/deposits .
Some possible considerations:
- Is this server behind a proxy? Do you have a proxy configured in config.inc.php?
- Does your PHP have cURL support enabled?
- Does cURL support HTTPS?
You can get details on the white screen at export by looking at your web server’s error log: