BuddyPress, "access permission" issue

Hi,
1. Yesterday, I installed BP through ‘Install Wizard’. So far, so good. However, the site’s current Users (including top-level Admins)are now unable to access the WP Admin. Major Bad!
Error: “You do not have sufficient permission to access this page”.
We are running MembersS2. (Not Multi-Site.) I assume this is an issue of Roles & Capabilities not being synched.

2. Also, our site currently has 50 members. How do we get them to show up as BP Members? It appears that if they login, they show up in the Member page. So, I assume that just the simple act of ‘login’ adds them to the Member List. But we would like to do it by default, so our users are not obligated to login to make this happen. any ideas?
3. We plan to import 200+members through the MembersS2 ‘import csv’. Will these new Members show up in the ‘BP Members’ area automatically?
https://www.gmtatennis.org