Cannot Install Required Plugins

I’ve just installed the theme at my website darkness.games but I am getting the following when trying to install some of the required themes (those not shown here were installed fine).

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Install Required Plugins
The installation and activation process is starting. This process may take a while on some hosts, so please be patient.

Installing and Activating Plugin Arcane importer (1/6)
Downloading installation package from https://www.darkness.games/wp-content/themes/arcane/plugins/arcane-radium-one-click-demo-install-master.zip…
An error occurred while installing Arcane importer: Download failed. cURL error 51: SSL: no alternative certificate subject name matches target host name ‘www.darkness.games’.

Installing and Activating Plugin Arcane redux (2/6)
Downloading installation package from https://www.darkness.games/wp-content/themes/arcane/plugins/arcane-redux-framework.zip…
An error occurred while installing Arcane redux: Download failed. cURL error 51: SSL: no alternative certificate subject name matches target host name ‘www.darkness.games’.

Installing and Activating Plugin Arcane types (3/6)
Downloading installation package from https://www.darkness.games/wp-content/themes/arcane/plugins/arcane_custom_post_types.zip…
An error occurred while installing Arcane types: Download failed. cURL error 51: SSL: no alternative certificate subject name matches target host name ‘www.darkness.games’.

Installing and Activating Plugin Arcane updates checker (4/6)
Downloading installation package from https://www.darkness.games/wp-content/themes/arcane/plugins/plugin-update-checker.zip…
An error occurred while installing Arcane updates checker: Download failed. cURL error 51: SSL: no alternative certificate subject name matches target host name ‘www.darkness.games’.

Installing and Activating Plugin Parallax backgrounds for VC (5/6)
Downloading installation package from https://www.darkness.games/wp-content/themes/arcane/plugins/parallax-backgrounds-for-vc.zip…
An error occurred while installing Parallax backgrounds for VC: Download failed. cURL error 51: SSL: no alternative certificate subject name matches target host name ‘www.darkness.games’.

Installing and Activating Plugin Visual composer (6/6)
Downloading installation package from https://www.darkness.games/wp-content/themes/arcane/plugins/js_composer.zip…
An error occurred while installing Visual composer: Download failed. cURL error 51: SSL: no alternative certificate subject name matches target host name ‘www.darkness.games’.

All installations and activations have been completed.

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