Not working not getting any debug either

Hi I had to disable the plugin and remove woocommerce as it was showing blank screen for checkout.

Now I enabled your plugin again and it says critical error and the pages won’t work.

These are the errors in my host:

Uncaught Error: Undefined constant "IDNA_DEFAULT" in /home2/danteste/domains/books.websitescreated.com.au/public_html/wp-content/plugins/octolize-australia-post-shipping/vendor_prefixed/guzzlehttp/guzzle/src/Client.php:195
plugins/octolize-australia-post-shipping/vendor_prefixed/guzzlehttp/guzzle/src/Client.php(101): OctolizeShippingAustraliaPostVendor\GuzzleHttp\Client->buildUri()
/plugins/octolize-australia-post-shipping/vendor_prefixed/php-http/guzzle6-adapter/src/Client.php(57): OctolizeShippingAustraliaPostVendor\GuzzleHttp\Client->sendAsync()

This continues for a very long time. What could be the issue please.