External player to view comics



Hi,
Not sure if I should post here or create a new thread as the last post was three years ago?
Anyway, what I have been trying to do is follow the methods described above and in the wiki for adding an external player to view comics. Although in my case, it is on a Nvidia Shield not a windows device.
Is it possible to use external players in Kodi on a Shield? So far I’ve failed in my attempts.
Firstly I installed CDisplayEX  on my Shield it works fine and is great at showing comics on my big screen TV in a way that is readable without have to zoom in and out on every page.
I then tried to add it in Kodi as an external player. Followed the steps in the wiki re playercorefactory.xml and the suggestions in this thread etc.

When I select an item to play and select ‘Play using…’ I see CDisplayEX as an option. However when I select it, I get this message on the screen:

External player active Click ‘OK’ when playback has ended

After a quick search, it looks like this has been mentioned a few times in the past, but I couldn’t find an answer/fix mentioned.
As a test I also added VLC player for videos creating another playercorefactory file but the same message kept appearing.
So my question is, has anybody successfully managed to add external players to a Shield or is it not possible?

I’m using Kodi Omega.