SSIS: Cannot convert between unicode and non-unicode string data types

Best thing to resolve this to add Data Conversion transformations to convert string columns from non-Unicode (DT_STR) to Unicode (DT_WSTR) strings.

You need to do this for all the string columns.

Add a data conversion task between OLEDB and EXCEL Destinations and do string conversations like below for the columns you are using

OLE DB provider "Microsoft.ACE.OLEDB.12.0" for linked server "(null)" returned message "Unspecified error"

OLE DB provider "Microsoft.ACE.OLEDB.12.0" for linked server "(null)" returned message "Unspecified error

or

ole db provider "microsoft.ace.oledb.12.0" for linked server "(null)" returned message "the select statement includes a reserved word or an argument name that is misspelled or missing, or the punctuation is incorrect.".

Here is the quick resolution for this fix, try run below commands in SQL Server

USE [master] 
GO

EXEC sp_configure 'show advanced options', 1
RECONFIGURE
GO
EXEC sp_configure 'ad hoc distributed queries', 1
RECONFIGURE
GO

This resolved my problem!