[Buryman26]

Just reset original firestick to factory settings.
I loaded ES File Explorer and Downloader.
I can download Kodi no problem. I can see it listed in both programs, but when I click to install it comes up Not Installed.
Any advice please?

[DarrenHill]

Where did you get the apk from, and which version did you download (32-bit or 64-bit)?

The correct one for the firestick is the 32-bit version - this one for Krypton 17.6.

Then of course you need to ensure that there's enough space on the firestick, and that you have install from 3rd party sources enabled (under the devices menu - settings > device > developer options > apps from unknown sources or something like that).