Spinning Circle on checkout - No transaction - Authorize.Net 1.0 community extension

[dmarketing]

Hi,

We installed the Authorize.Net 1.0.0 extension from Magento Marketplace.

authorizenet/magento-module-authorizenet

We are able to create and void transactions using direct post.

However, when trying to checkout with the magento-module-authorizenet extension, we get a spinning circle with no error.

Also, I do not see anything in the payment log.

In addidtion, when I tried to use the "Authorize.net Configuration Wizard", I get "Attention. An error occurred"

Please help.

Thanks,

Mike

[dmarketing]

From Conole after pressing checkout...

Fatal error: Uncaught Error: Class 'Symfony\Component\Yaml\Yaml' not found in xxxxxxxxxxxxxxxxxxxx/vendor/jms/serializer/src/JMS/Serializer/Metadata/Driver/YamlDriver.php:20