We have added a new functionality that allows you to show only reviews with media on your site.
That means that when that functionality is turned on in these 3 steps below on your customization page:
You will only see reviews that have photos or videos attached. You won't see reviews that are only text and don't have photos or videos attached.
That may be why your reviews (ones that contain only text and no media attachment) don't show on your site.
To get them to show again, you could follow the same steps to turn the function off, then you can have text reviews, as well as reviews with media, showing on your site.