How to update the default fallback topic to my own topic?

[Lisa71]

I want to update the default fallback topic to my own topic, however, I can't find my topic in the "custom topic" list, what's the criteria for displaying my own topic in the fallback topic selection list? THanks. 

[Tanushree Maiti]

Please refer this links, see if it helps you:

Maximizing Relevant Content Display in ServiceNow ... - ServiceNow Community

Fallback in virtual agent - ServiceNow Community