Campaign Responses is greyed out in the listener step in Eloqua program

Summary: Campaign Responses is greyed out in the listener step in Eloqua program

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I want to create a eloqua program to capture campaign response and send to our CRM system. The first step in the program canvas is the listener step to 'listen' to the campaign response, however, when I select the source, "Campaign Responses" is greyed out. See the screen shot.

There is no other program in the instance and could anybody help me what I can do to enable this.

Thanks

Yi Wang

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