Usually, there are only a few things that could cause your Social Inbox to stop pulling posts.
The first thing to check is if your social accounts are connected. If they aren't connected, no content will pull from any platform. Read this article to learn how to connect your social accounts.
Next, check your Keywords. These words can't contain any symbols or spaces. For example, if you've added a keyword like, "bam_bams_bbq", it will create an error. Check your keywords and make sure they only contain letters.
If your keywords look good, the next issue could be the Facebook/Instagram connection. In order to aggregate content from Instagram, two things need to happen. First, your Instagram should be a Business Account. If your Instagram isn't a Business Account, read this article to learn how to change a personal Instagram to a Business Account. Second, you have to make sure that you have a page associated with your Facebook account. Your Social Inbox will not pull posts if you do not have a Facebook page selected.