Normally VLOOKUP is an inbuilt function which is available in MS-excel sheet and used to search the data in vertical column of index.
Step-by-step explanation:
IFERROR functions returns error means search data type is invalid. In this scenario invalid staff id means either staff id data type is mismatch.
These scenario happens when end user search string data in numeric column of staff id. End user has to correct the staff id data type from string to numeric. Some cases the staff id has invalid data such some special characters are used, such as “-“,”=” etc.
End user has to remove special characters in staff id column and check whether VLOOKUP gives error.