Salesforce Einstein BOT No Agent Dialog for Messaging for In-App and Web feature will be invoked when the Outbound Omni-Channel flow couldn’t transfer the Session from BOT since no agents are at capacity to handle the session.

Outbound Omni-Channel Flow:

Check Availability for Routing is used to check the Agents Availability. 

Decision block is used to decide whether to route to the Agents based on the No of Online Agents value. 

Route Work is used to route the Messaging Session to the Queue.

BOT Outbound Omni-Channel Flow:

BOT Transfer to an Agent Dialog:

BOT No Agent Dialog:

Output: