Invalid Request. The Product Id Was Empty. Activation Error.

If you run WordPress Multisite and network activate WooCommerce Amazon Fulfillment and WooCommerce you may receive the error below when trying to activate your license:

WooCommerce Amazon Fulfillment Invalid Request. The Product ID was Empty. Activation Error.

We believe this is due to a WordPress bug when network activating WooCommerce Amazon Fulfillment and WooCommerce.

If you activate both WooCommerce Amazon Fulfillment and WooCommerce per site (instead of network activating) that should resolve the issue and allow you to activate your license key and email.