Notice upon activation on Plugins page

I am getting the following notice at the top of the Plugins page when activating the latest version of the AgentPress Listings plugin:

The plugin generated 200 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.

Running latest Genesis and AgentPress theme, no other plugins activated.

https://www.ads-software.com/plugins/agentpress-listings/