Check out this tutorial for how to allow Flash content in Chrome
Google Chrome now blocks Flash content automatically, so it sometimes blocks content that you want to be able to see. Use the steps in the above tutorial to fix this.
Log in outside of Canvas or via an LTI link:
Close your browser and restart it
Point your browser to: https://uw.voicethread.com and follow these log in directions
Go to the Learning Technologies Canvas site and click on the VoiceThread home link on the left sidebar.
If your Canvas course has a Course VoiceThreads link in the left course navigation, click the link to log in to VoiceThread.
Navigate back to your Canvas site, refresh your browser and try clicking on the VoiceThread presentation you would like to watch.
You can replace a slide in your VT presentation without deleting comments.
Use this strategy to replace the contents of a slide and still keep all of the comments on that slide. Remember that this is done on a slide by slide basis so you will have to create a separate PowerPoint, PDF or image file for each slide.
More than likely this is being caused by a permissions issue. This usually occurs when a thread is setup as a private thread, viewable only by course members. Go back and click on a VT link that will log you into VT and then return to the page with the embedded thread.
Click on the "hamburger" menu in the top, left of the thread.
In the resulting menu, click on the "Share"option. A new tab will open with the share options for this thread.
Click on the "Copy Link" button.
Paste the link into another tab in your browser.
There are several methods for making copies of existing VT presentations. When making a copy, you will want to check the sharing settings and update if necessary.