We are using the Bedrock setup which disables the plugin installation from the admin area so I can not access the commercial tab to add the key.
So I found a way to do it with OTGS_INSTALLER_SITE_KEY_WPML (From the previous responses of the WPML forum) from wp-config.php so I have added that to my .env file and done the required changes to my wp-config.php and I confirm the key is accessible.
Please help me resolve the error.
You are using an invalid site key defined as the constant OTGS_INSTALLER_SITE_KEY_WPML (most likely in wp-config.php). Please remove it or use the correct value in order to be able to register correctly.