This error is most often related to the server configuration!
Contact your hosting company and ask the hosting support to check the following points:
- The server is running a recent version of PHP and the cURL library.
- Increase PHP Memory Limit settings.
- Ask your web host if there is some limitation with wp-cron, or if loopback is disabled.
- Ask your WebHost if there a firewall or security module (e.g. mod_security ) that could block outgoing cURL requests.
- Your hosting company might need to switch DNS configuration to something like OpenDNS.