This issue is caused by a hosting limitation enforced by your hosting provider.
The error returned by the plugin during running is: curl: ‘Connection timed out after xxxx milliseconds’ – this means that it does not manage to connect to outside servers, probably because it’s connection is blocked by a firewall rule.
Some of the plugins also support the setting of proxies, in ‘Main Settings’ -> ‘Web Proxy Address’. If your plugins supports this feature, you can try setting different proxies here, to see if any will work.
If you don’t know proxy servers, or they don’t work, to solve this, you should contact your hosting provider’s support and ask them to allow the plugin to connect to external hosts (to open outgoing ports for your website, for all external IP addresses).