Why am not able to activate my WP Offload license key?

Hi,

We have purchased the WP Offload License key but not able to activate it.
I get the below error message on the plugin page.

Could not connect to deliciousbrains.com — You will not receive update notifications or be able to activate your license until this is fixed.
This issue is often caused by an improperly configured SSL server (https). We recommend fixing the SSL configuration on your server, but if you need a quick fix you can:

Temporarily disable SSL for connections to deliciousbrains.com

I have also added this in wp-config.php file
define( 'DBRAINS_API_BASE', 'https://api.deliciousbrains.com' );

Can someone help here?

Regards,
AG.