It may be difficult to determine the cause without having the ability to view the page where the feed is installed. The underlying cause could be CSS that is being over-ridden by theme’s CSS or some other source.
Is it possible to provide a link to the site page where the feed is installed? If you do not wish to publicly provide a link you can submit a request for support privately from our support page here.
Also, depending on the location of the space there are two plugin settings where a user can control the amount of padding between some of the feed’s components although there isn’t a padding setting for the actual space “between posts”.
You can find theses settings by going to your WordPress Dashboard – Facebook Feed – Customize – and you will find under the …
General tab – you will find the “Feed Padding” which sets the amount of padding/spacing that goes around the feed.
Typography tab – you will find a padding setting under the “Header” section which sets the amount of padding/spacing that goes around the header.
