Have you updated Show Box at all? When you see this sort of message:
Click Update. Next this screen should appear:
Click Install.
If you see an error message about security settings, or don't see the install window above, head to the launcher's homescreen, then click:
Settings
Other tab
More Settings
Security
Tick the Unknown Sources box and press the home button on your remote
Click the circle with six dots or My Apps and open ES File Explorer.
Get past the intro screen and expand the LOCAL menu on the left.
Click the Download link.
You should see something similar to this:
Click on show_box.apk then Install, then Install again.
I was running version 3.6 (to check start from the homescreen and click Settings, Other tab, More Settings, Apps, scroll down to Show Box and click it). I think 3.6 might be the version my T8's firmware originally installed.
I'm now running 4.08
After this, the newest films work.