You have one or more Agents registered in the database for which no corresponding definition is available in the source code:

<% @undefined_agent_types.each do |type| %>
• <%= agent_type_to_human(type) %>
<% end %>

The issue most probably occurred because of one or more of the following reasons:

• If the respective Agent is distributed as a Ruby gem, it might have been removed from the ADDITIONAL_GEMS environment setting.
• If the respective Agent is distributed as part of the Huginn application codebase, it might have been removed from that either on purpose (because the Agent has been deprecated or been moved to an Agent gem) or accidentally. Please check if the Agent(s) in question are available in your Huginn codebase under the path app/models/agents/.

You can fix the issue by adding the Agent(s) back to the application codebase by

• adding the respective Agent(s) to the the ADDITIONAL_GEMS environment setting. Please see https://github.com/cantino/huginn_agent for documentation on how to properly set it.
• adding the respective Agent(s) code to the Huginn application codebase (in case it was deleted accidentally).
• deleting the respective Agent(s) from the database using the button below.

<%= link_to icon_tag('glyphicon-trash') + ' Delete Missing Agents', undefined_agents_path, class: "btn btn-danger", method: :DELETE, data: { confirm: 'Are you sure all missing Agents should be deleted from the database?'} %>