You can request a passphrase  reset on the login form in the desktop client or on .

If you have previously created a recovery key, using this will allow you to retain your contacts, groups and shared content.  

If you do not have a recovery key, you will be able to reset your passphrase as long as you have access to your two-factor authentication codes. 

When you reset your passphrase this way, new encryption keys will be generated, and you will lose access to your existing messages, files, contacts and groups. Your contacts will be informed that you have re-set your passphrase and your keys.