Hi Amely,
do you use the same driver file in KNIME 3.7 and KNIME 4.1? Maybe you need to register additional jars to connect to your Oracle database e.g. when using Oracle Wallet?
If this is the case you can unzip the driver jar and all of its companion libs into a directory and then register the complete folder via the Add directory button as shown here
You can also add the jars separately via the Add file button like this:
Bye
Tobias