A merge field in your OmniScript renders blank at runtime even though the Data Mapper preview returns the data correctly. How do you troubleshoot it?

This is the most common OmniScript defect and it is almost always a path or timing problem rather than a data problem.

1. Compare the response JSON to the merge field path. Open the action's response in preview and check where the value actually lands. A Data Mapper frequently nests output under an object node while the merge field is written as if the value were top level.
2. Check the element name, not the label. Merge fields resolve against element names. Renaming a label in the designer does not change the underlying name, and duplicating an element can silently produce a name you did not expect.
3. Check ordering. A merge field on the same Step as the action that populates it may render before the response arrives. Move the display to a later Step or ensure the action runs on Step entry rather than on exit.
4. Check the running user. If the field is protected by field-level security, the Data Mapper returns nothing for that user even though it worked for you. Test as the actual persona, not as a System Administrator.
5. Use the preview data JSON panel. Watching the data JSON build up as you move through the script tells you immediately whether the value is absent or simply in a different place.