‘Activity’ and ‘Groups’ menus are protected by ‘bp_moderate’ virtual user capability, which finally mapped to the ‘manage_options’ capability. ‘Users->Site notices’ and ‘Privacy’ menu item under ‘Settings’ are protected by the same ‘manage_options’ capability.
Check if ‘manage_options’ was granted to your ‘administrator’ role.
If problem still exists, then deactivate all plugins. Will it help? Activate plugins back one by one to isolate the problem.
Try to change theme to WordPress 2017. Will it help?
