If the ERROR.TYPE function in Excel not working for you, ensure the formula is correct, check for errors in the referenced cell, or repair Excel.

Microsoft Excel: How to Find Missing Numbers in a Sequence. Locating missing sequential numbers can be an arduous task when working with long lists of data. For example, you might want to locate ...

To make the lookup more specific—useful if your DGET keeps returning the #NUM! error due to there being more than one match—you can use more than one criterion in argument c.