You should always try to read the release notes of releases, specifically the following: https://www.scirra.com/construct2/releases/r179
[quote:23g9j6fw]Please note from this build CocoonJS support is deprecated. You can continue to use it for existing projects by right-clicking the Insert Object dialog or Export Project dialog and selecting 'Show deprecated plugins/exporters', however the options are now hidden by default to discourage new users from going down that route. CocoonJS has a number of difficult compatibility problems and bugs which do not appear to be likely to be fixed and cause constant complaints from users. We instead recommend using Ejecta for iOS and Crosswalk for Android. From iOS 8+ and Android L+ we instead recommend using PhoneGap, which from those versions have full GPU-accelerated WebGL and Web Audio support on both platforms, much better compatibility due to being real browser engines (with form controls, XML parsing, letterbox scale, etc), and low filesize overhead. We're aware that IAP and advertising support still needs to be added to PhoneGap (at least officially) and plan to address this before the next stable update.
So as it says, the option has been deprecated, but is still available if needed.