When using the twitter login, after setting up the twitter

When using the twitter login, after setting up the twitter app, of course, my site directs ppl to this link to login via twitter: http://my.domain.com/?&wpmudev-chat-action=pop-twitter -- doesn't popup a login page (like facebook and google+, both of which work fine on my chat) and the page is blank.

Some help would be greatly appreciated.

(I am using the latest version of chat, 2.0.6.3.)

Thanks.