If the add-on isn't working for you, try these steps
This is for when you're suddenly back to new twitter or never got back to old twitter. For other issues check known issues below or submit a new issue.
First, try hard refreshing twitter. Shift+Click on reload in the twitter tab.
If that didn't work, try reinstalling goodtwitter by going to the store page, clicking remove then installing it again.
Next, try clearing cookies for twitter. Click on the lock, then click cookies. Now just click remove NOT BLOCK for ALL OF THEM. You'll have to log back in. That should fix most issues.
You can also try restarting chrome or your computer.
If all that didn't work create an issue on GitHub here
This happens sometimes. Shift+Click on reload and it should be fixed. Refer to issue #9.
No fix yet. Issue #6.