It is virtually impossible to detect every server which our theme tries to use because we have a section called Extensions that retrieves information from their respective plugin developer and those IPs may change and it is not on our hands.
You will need to contact your hosting service provider and ask them to open up all connections for you. Then kindly install whatever plugin you like from X > Overview section extensions.
Please kindly consider that this kind of blocking will not only affect our theme but any other third party plugin that you may install using the cURL functionality.
This is too much limitation for a hosting service provider and I wonder why a Wordpress installation needs such tight security. Anyway, unfortunately, there is nothing we can do for you at this stage and this is something you should resolve contacting your hosting service provider.
Thank you for your understanding.