extension icon not showing on Chrome

[NateJBeck]

likely newbie issue here, but can't get Kindle extension to work

using ubuntu 14.04

• installed chromium
• installed kindle for campfire as extension

After installation the icon shows up briefly with this message:

• "This icon will be visible when the extension can act on the current page. Manage your extensions by clicking extensions in the tool area."

Went to extension manager - looks good - "enabled" etc. Have tried resizing address bar to no avail.

Any suggestions?