By default MQTT Engine is configured to block writes. You can change this on the general tab per this doc: ME: Configuration - MQTT Modules for Ignition 8.x - Confluence
Specifically, you need to uncheck the ‘Block Node Commands’ and ‘Block Device Commands’. This will ensure that MQTT Engine generates CMD messages to the Wago device.
In order for this to work, the Wago device will need to be able to consume these messages and write to the outputs. You may need to get in touch with Wago to see how this is configured on that device.