The Merge (Data Management) tool returns null values when the input data is added from the drop-down option.

Workaround

Use one of the methods below to resolve the issue:

• Use the Append (Data Management) tool.
• Add the data to the Contents pane and drag the layers to the Merge tool.
• Add the input dataset by using the drop-down option and click 'Reset' on the Field Map of the Merge tool.

Steps to Reproduce