Dis you create some users manually? The reason why you can’t see them is because BuddyPress will only show members considered as “active members” on the site. Even if you manually activated the users, you need to log in with each user account at least once so that BuddyPress considers them as active members.
To make it easier for you, you can install the “User switching” plugin (https://wordpress.org/plugins/user-switching/). This plugin will allow you to browse your members list, then click on “Switch to” on the user of your choice. After switching, a link will appear at the bottom of your site to switch back to your admin user. You can then repeat the process for all your users and they should appear in your members page.
If you have Paid Membership Pro plugin activated, this issue could also come from its misconfiguration (and its BuddyPress add-on’s). Please make sure to deactivate Paid Membership Pro (and its BuddyPress add-on) to test if this is related to the configuration of these plugins.
If this is the case, we recommend that you follow this post explaining how Paid Membership Pro and its BuddyPress add-on work:
Hope this will help. 🙂