In January 2020, we released a new version of Nelio A/B Testing that introduced several improvements and new features. On the one hand, Nelio A/B Testing 5.0 uses the new technologies provided by WordPress and thus comes with a faster and friendlier user interface—defining tests and monitoring their progress is now easier than ever. On the other hand, we’ve completely rewritten the plugin from scratch so that alternative loading and event tracking is faster and more reliable.
When upgrading your Nelio A/B Testing plugin to version 5.0+, you’ll be first presented with a welcome screen:

If you had created a few tests with previous versions of Nelio A/B Testing, you’ll be presented a slightly different version of the welcome screen:

In this particular case, Nelio A/B Testing needs to transform your old tests into the new format used by Nelio A/B Testing 5.0+. When updating tests into the new format, the plugin will also migrate the results of your finished and running tests.

This process may take a few minutes (depending on the number of experiments you have). Please make sure you have a backup of your site before proceeding with the update—if something went wrong, you’ll need a backup to recover your old tests and use the previous version of Nelio A/B Testing.