If you do not get the expected value in Excel, you may be left without an error message that would guide towards the cause of the problem.

In order to see the related status and error messages, you can add cells that refer to this information. To do so, from Connectivity Explorer, drag-and-drop or copy-and-paste (in addition to the formula you already have) also the cells under "Quality" (OPC Classic), "Status" (OPC UA) and "Error Message" columns.

You can also create formulas that combine either the value, or the error message in the same cell, depending on a condition. Refer to Topic Syntax and Result Value Selector for more details.