Hey @Anonymous
As @VJR said - can you share your code? What exact errors you get and where? Opening connection or executing the query?
Are you able to do simple select like this?
SELECT * FROM [SheetName$]
Also, are you sure you use correct insert statement like one below?
Insert into [SheetName$] ([Column1],[Columns2]) Values ("Data1","Data2")
Remember to close SQL connection to actually save the changes.