I had limited success by downloading fresh copies of bootstrap.bundle.js, bootstrap.bundle.min.js, renaming them as bootstrap.js, bootstrap.min.js and replacing the original files in ...activello/assets/js/vendor/
After this, the nav-bar opens up for a fraction of a second, but collapses instantly. 🙁
I finally gave up and installed version 1.4.2 of the theme – this issue isn’t present on that version.
Download the older version of the theme from wordpress.org – https://downloads.wordpress.org/theme/activello.1.4.2.zip
