If you are updating from a very old version of Ninja Forms (any version older than 2.9), you will probably experience issues updating directly to the newest version. This document will get you caught up to current without breaking things!
Below we have listed each major version of Ninja Forms prior to the 3.0 upgrade. If you’ve already tried to update from a very old version and things have broken, find the version your site is/was running from the list below, delete your current plugin and reinstall that (don’t worry, you won’t lose your forms or submissions). If you haven’t tried to update yet, find your version below and download/install the version one step higher after deleting your current version (again, you won’t lose your forms or submissions).
Then, move through each version deleting/downloading/installing one by one up the list until you get to the most recent on this page (Ninja Forms Version 2.9). Once you are on 2.9, you should be okay to run the update to the most recent version from your WordPress dashboard. Once fully updated, use this article to convert from Ninja Forms 2.9.x to Ninja Forms Three.
Ninja Forms Version 2.9 – August 30th, 2016
Ninja Forms Version 2.8 – December 18th, 2014
Ninja Forms Version 2.7 – August 19th, 2014
Ninja Forms Version 2.6 – June 10th, 2014
Ninja Forms Version 2.5 – March 24th, 2014
Ninja Forms Version 2.4 – January 23rd, 2014
Ninja Forms Version 2.3 – December 22, 2013
Ninja Forms Version 2.2 – October 28, 2013