Fatal error when plugin is activated

I have a Pantheon server where I’ve recently activated this plugin and the frontend dies with this error and an FTP message:

Connection Information
To perform the requested action, WordPress needs to access your web server. Please enter your FTP credentials to proceed. If you do not remember your credentials, you should contact your web host.

Hostname 
127.0.0.1
FTP Username 

FTP Password 
 This password will not be stored on the server.
Connection Type
 FTP  FTPS (SSL)

Fatal error: Uncaught Error: Call to undefined function wp_create_nonce() in /code/wp-includes/functions.php:1828 Stack trace: #0 /code/wp-admin/includes/file.php(2267): wp_nonce_field('filesystem-cred...', '_fs_nonce', false, true) #1 /code/wp-content/plugins/wpshopify/classes/filesystem/class-filesystem.php(36): request_filesystem_credentials('', 'ftpext', false, false, Array) #2 /code/wp-content/plugins/wpshopify/classes/filesystem/class-filesystem.php(77): WP_Shopify\Filesystem->maybe_init_wp_filesystem() #3 /code/wp-content/plugins/wpshopify/classes/compatibility/class-manager.php(20): WP_Shopify\Filesystem->bootstrap_filesystem() #4 /code/wp-content/plugins/wpshopify/classes/factories/compatibility/class-manager-factory.php(19): WP_Shopify\Compatibility\Manager->__construct(Object(WP_Shopify\Filesystem), Object(WP_Shopify\DB\Settings_General)) #5 /code/wp-content/plugins/wpshopify/classes/factories/processing/class-database-factory.php(39): WP_Shopify\Factories\Compatibility\Manager_Factory::build() #6 /code/wp-cont in /code/wp-includes/functions.php on line 1828

Deactivating the plugin resolves the issue. Any ideas how to trouble shoot?