aha, there was another discussion on the same topic. The initial instruction could be clearer. DO NOT LEAVE callback URL blank! Use your full website address incl 'http://'
It resolved the issue I had. Thanks.
See full text below:
Log into the admin section of your site. Under settings (in the left menu) click "Twitter Widget". There should be a direct link to this page in the admin notices that tell you your consumer key isn't set up.
Once there, you'll see several meta boxes. The top one is labeled "Authenticated Twitter Accounts" and we'll deal with that in a minute. The second is labelled "General Settings" and has two fields labelled "Consumer key" and "Consumer secret". Under those fields are step by step instructions for how to obtain the info to put into those fields. Here they are copy/pasted:
Add a new Twitter application
Fill in Name, Description, Website, and Callback URL (don't leave any blank) with anything you want
Agree to rules, fill out captcha, and submit your application
Copy the Consumer key and Consumer secret into the fields above
Click the Update Options button at the bottom of this page
Make sure to pay attention to step two and do NOT leave the callback URL field blank. Use your site address (or any other valid URL).
Once those are saved, look back at the first box labeled "Authenticated Twitter Accounts" and click the "Authorize New Account" button. This will take you to Twitter and ask you to authorize the app that you previously created. Once you've done that, you will be forwarded back to the settings page and you'll see your Twitter account listed in the top meta box. Repeat the instructions in this paragraph to authenticate additional accounts if needed.