It appears that the project manager is only allowing observations by the following people to appear in the project:
Have you tried reaching out to the project manager? Whether this is a bug or intentionally limiting to this list of people, I’m not sure. These people should be displayed on the “About” page, but it doesn’t. https://www.inaturalist.org/projects/flora-and-fauna-of-the-southbelt?tab=about I was only able to see it by checking the json (https://www.inaturalist.org/projects/flora-and-fauna-of-the-southbelt.json) or when trying to join the project.