Could it be the application URL that's incorrect? http://mydiskstationip:5000

I decided to try the Github plugin and now I can successfully search for movie info and poster. However the cover fails to download. Https://image.tmdb.org.......

@johnmorrell@live.co.uk said:
No search results show as there is a problem with the plugin.
When testing the plugin connection it reports
"Connection failed. Please make sure the API key you entered is correct and check your Internet connection "

Your API Key is working correctly considering the test you did.
If you didn't find any help in the chat links I sent, then I believe that only Synology support will be able to help.

Thank you for your support, it's greatly appreciated. This was the solution...

Disable IPv6 on your NAS, as this has been known to cause connectivity issues with the Video Info Plugin: Go to Control Panel > Network > Network Interface. Select your LAN interface and click 'Edit'. Navigate to the IPv6 tab and set IPv6 setup to 'Off'. Click 'OK' to save the changes. Ensure your NAS has a stable internet connection and that the DNS settings are correctly configured: Go to Control Panel > Network > General. Tick the 'Manually configure DNS server' checkbox. Set the DNS server value to '8.8.8.8' or '8.8.4.4'.

After applying the settings metadata was successfully applied and the default plugin also connected successfully. Hope this helps anyone else having this issue