SQL parameters were detected, but no parameters are being supplied. Example:
conn.Execute("update Customers set Name=@name where Id=@id"); // note no args supplied
If the SQL variant is not known, then it may mistakenly report local variables as parameters in some scenarios, for example:
conn.Execute("""
declare @id int, @name nvarchar(200);
-- assignment not shown
update Customers set Name=@name where Id=@id");
If possible, specify the SQL variant.