Still says app not loaded. When I click done it shows file was successfully loaded to /sdcard/Download/Downloader with the app address. But my firestick 4K does not have a sd card.
I look at files on Downloader and it shows the install file. Try loading from there it also says app not installed.
I tried to install a kodi fork from your toolbox and that also will not install.
Downloader install unknown apps is turned on.