Sorry if I'm bumping this thread a bit late, but it seemed a similar issue for me.
I had a difficult time with my first login. Keychain and Steemconnect both failed to work in the Brave browser, Steemconnect failed in Safari, but I was finally able to login with Steemconnect in Firefox. So I'm wondering if there may be browser compatibility bugs at the moment. All this is on Mac OS 10.14.3
Just my observations, thanks much for the hard work!