Updating sql table in R using library(odbc) returns error: external pointer is not valid

I am trying to perform:

con <- dbConnect(odbc(),
                 Driver = "SQL Server",
                 Server = "myServer",
                 Database = "myDataBase",
                 UID = "myUser",
                 PWD = "myPassword")

dbSendQuery(conn = con, 
            "INSERT INTO etl.VALOR_ETL (INTCODIGO,SERCODIGOEXTERNO,VALDATA,VALVALOR) 
             VALUES ('Generica', 'TESTE', '2018-01-01','2')" )

However, I get the following error:

Error in new_result(connection@ptr, statement) : 
external pointer is not valid

I have tried other packages, however, I could not find any other one that allowed to query "insert into".

What would be this issue related to?