RSS feed not updating

I’m having trouble with my rss feed not updating, which has stopped my mailchimp RSS e-news from sending.

Until a few hours ago, the feed was showing the latest post as one from the 10th August, but now I can see the latest one, however, if I validate my feed the latest one is still the one from the 10th.

I am using a plugin, Featured Images in RSS w/ Size and Position but even with it deactivated the feed validation doesn’t show the more recent posts.

Any ideas, greatly appreciated.

Thanks,
Belinda