I did have it config before updating
Question was if you've saved the config file. That is a best practice when upgrading your server. Do some search on the forum and refer to the manual for more information.
If you have it running before, there is a good chance you can access the previous installed environment, if you wish.
Turn the server on and when the FreeNAS boot appears, press the space bar to pause the boot. You will see four options. Option 4 says: Select Boot Environment - press 4 to activate it.
On the next screen you will have a list of previous envioronments, select the previous one before upgrade and you should be back. Below the ones from my server: