can't log into wp-admin of mapped domain

okay, I set up a new multisite install with the domain mapping plugin according to the posts at:

https://www.ads-software.com/support/topic/multiple-multisite-installs-on-single-ip

https://ottopress.com/2010/wordpress-3-0-multisite-domain-mapping-tutorial/

https://codex.www.ads-software.com/Create_A_Network

I tried logging into /wp-admin/ of the first mapped domain, and I keep getting the message:

Greetings Site Administrator! You are currently allowing “none” registrations. To change or disable registration go to your Options page. Registration has been disabled.

instead of the wp-admin login screen.

what am I missing???