I have two test websites running latest version of Joomla. In one environment I have upgraded Forms to 1.6 by downloading the ZIP file from the website. Under Extensions I used Install to install this new version. I do not use Joomla caching, logged out and logged in, deleted browser history. But unfortunately I can not see the list of languages. When I click on the Language button, I see an empty list.
However, on my second test website I used the built-in method to upgrade Forms. After the upgrade I logged out and logged back in. When I go to the Language screen I can see a full list of languages. Same browser, same computer.
I re-installed Forms on the first test website, but no success.