I have installed BuddyPress to a fresh WordPress (default theme) and it adds “Activity” + “Members” with out any issue, but it does not add the “Register” page to the navigation.
The register page is installed to the website, but it does not appear in the navigation. I have set the proper fields in the “Pages” tab of the BuddyPress settings.
It is the default wordpress theme. I added it to the navigation but it removed the other two options. Although it just hit me that I can add the other two pages on the navigation.