You’ll have to fill out the bug report for anyone to be able to help you. Particularly, telling us which project you’re referring to and which observations you think should be in but aren’t.
It is a collection project, so you can’t add observations to it. They will be added automatically if they meet the criteria.
You have set it up so only observations by a certain list of 10 users will be collected. The list does not include yourself. There are 26 members of the project - so more than half of them aren’t in the list of users whose observations will be collected.
Either add all the members to the list, or set the project so that it collects observations by “Project Members Only”.