Plug-in deployment error using on-prem Appian

I am developing a custom smart-service and exported the project to a JAR file under the _admin/plugins folder. 

On start-up, I received the following error: 

2019-02-11 21:38:18,314 [Appian Plugin Hot Deploy] ERROR com.appiancorp.plugins.LoggingPluginEventListener - Failed to load Plug-in 'Unknown-1518766036' (Unknown-1518766036) version 0.0: 'Unable to load plugin: Unable to process plugin to generate OSGi manifest'

Caused by Null Query

Any ideas what might be causing this issue?