Buongiorno!
Im using jwplayer 7 and its working fine with the code below wich I got from the jwplayer demo site:

related: {
      file: "https://content.jwplatform.com/related/C4lp6Dtd.xml"
   }

but I cant get the feed wich your plugin generates.

Im trying https://localhost/archives/category/action/?feed=related-feed

of course I have updated and checked the permalinks if are correct.

Please can you guide us how to get it working?

https://www.ads-software.com/plugins/related-videos-for-jw-player/

you are saying that:

In your JW Player code, you’ll have something like that

‘related’: {
‘file’: ‘https://YOUR-SITE/archives/category/THE-CATEGORY-SLUG/?feed=related-feed’,
‘heading’: ‘More videos!’,
‘onclick’: ‘link’,
‘dimensions’: ‘210×161’
}

but where is JW player code? which file you mean? how can I check this?

https://www.ads-software.com/plugins/related-videos-for-jw-player/