Examine the Shapesheet of the callout target to verify the actual name of the Shape Data property. The label might be IPAddress but its 'name' might not match that. For instance, you might find that =CALLOUTTARGETREF()!Prop.Row_1 works whereas =CALLOUTTARGETREF()!Prop.IPADDRESS does not.

In the shapesheet, you look at the Shape Data and find the red text in the first column. That is the text you should be using in your field. If you pick a properties name rather than its label it should behave as advertised.

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Andrew Lockton
Chrysalis Design, Melbourne Australia