According to https://developer.mozilla.org/en-US/docs/Web/Events/input, the only browser that triggers "oninput" callbacks for checkbox HTML elements is Firefox (versions later than 49).
Here: https://github.com/vladimiroltean/lbt/blob/master/js/client.js#L149 is the "oninput" callback that will not get called on all other browsers.
The available workaround is to manually log in into the server, edit the flows.json file and set "enabled": true for the desired flows, then restart the application.
The proper fix would be to use a different DOM API for checkboxes that reacts to clicks and is more browser-interoperable than oninput is.