As of 9/5/2018, all Research Computing systems require Duo authentication to login. To get Filezilla to work with a Duo enabled system, you need to specify an "interactive" connection. This is done by using the Site Manager option to create a new "site" within FileZilla. Site Manager is the first option under the File menu. Create a new site, specify the host (for example nobel), SFTP as the protocol, Logon type as "interactive", and your netid. Save the site and click Connect.
First you will be prompted for your password. Next you will get a prompt for a Duo option. This is the standard Duo prompt, choose whichever option you usually use (e.g. 1 to get a text message). After you confirm with Duo, you should be connected.