[تم الحل] Connection to WPML.org

Background of the issue:
I am working on my development site, staging.e-alouminio.gr, and have registered e-alouminio.gr as my production site. I am sharing credits between these two sites.

Symptoms:
In e-alouminio.gr, I receive the message 'WPML plugin cannot connect to wpml.org' despite seeing 'WPML is registered on this site'.

Questions:
Why does the WPML plugin show a connection error to wpml.org on e-alouminio.gr?
How can I resolve the connection issue with WPML on my production site?