If you are upgrading from version 1.x to 2.x, you should first delete the "hipay" folder which is located at "modules/gateways/hipay". This way, al leftovers from the previous version are deleted.
After this, you can upload the new files to "modules/gateways/", and continue the installation as described here
You don't need a new license key. You can use the existing v1 license key. If you have any license issue, please reissue your license as described here
, or contact support.