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How to clear browser cookies, history, temporary files and clear proxy cache



Many issues in Plato Courseware can be resolved by following these four recommendations. Please try these suggestions and see if your issue is resolved. If you are unable to perform these tasks due to admin restrictions, please contact your school's IT department.

3. Add Trusted Sites for Internet Explorer

Directions for adding Trusted Sites

4. Flush DNS for Windows Workstations

Directions to Flush DNS

Note: After performing the flush, we recommend that each machine have the temporary internet files cleared.


What's Next

Start the activity again and verify that it loads properly. If an activity is not loading and/or images not appearing on test, try flushing the DNS using the steps above.

Note: If the computer is in a customized network configuration, such as at a school or connected to a virtual network via VPN, the network’s DNS tables may need flushed or updated. Please contact your network support for assistance in this process.

Each website consists of hundreds of thousands of files that load at once to display content in your browser. In order to speed up the loading process, your browser will try to ‘save’ pieces of that site or that site’s ‘files’.  Because your browser can  display those files that are stored in its cache much faster than it can pull the ‘fresh’ file from a server, the next time you visit the site the use of the cached files will help cut down on loading times.


Occasionally web developers will have to make updates to the files that make up a site.  Usually this is done if they need to implement a fix or to push out a new feature for that site.  When a file that your browser has cached is fixed or updated, accessing that site won’t pull the most recent file and you might not see the most recent changes.

Additionally, when your browser has saved too many files from the websites you’ve visited it can become clogged with the cached information stored.  This will cause slow load times and pages that don’t load correctly. By clearing your cache it erases all previous stored files from sites you’ve visited.


Clearing the cache frees up the temporary memory on your computer allowing it load the newest versions of the sites you are visiting.

Error Message

Some errors and issues you may encounter are:

  • "No Active Product Memberships" error
  • Activity stuck/lock/freezes or returns to login page
  • Browser runs slowly or crashes
  • Temporarily Unable to Communicate with Server while running lessons
  • A yellow triangle with a "!" appears during your lesson
  • Your user information was incorrect when trying to log-in after password reset
  • Unable to access a Web site when using Safari browser
  • Unable to see navigation tools at the bottom of the tutorial using Safari browser
  • Server error in '/' application" when launching activity
  • Error: "Load Failure. Trying again." or "Failed to load Container swf wpmtier/containers/funcontainer.swf"
  • Unusual or incomplete display of graphics accompanying text in lesson or test in PLE
  • ERROR: "Xtras Package Download Error" when launching Job Skills for the Real World lesson
  • ERROR: "Can't establish a secure connection to the server" when accessing using Safari
  • Attempting to view a report in PDF format opens to a blank screen
  • Login page reappears when trying to login
  • Tabs or options not visible; affects a variety of tasks
  • Environment launch data error 2
  • ERROR: "The system has encountered a significant error" launching content
  • Incorrect graphics appear in place of properly used punctuation marks when creating announcements
  • ERROR: "File extension is not supported" when uploading Digital Drop Box Activity


Clear Cookies

What to do if you're using a proxy server

If emptying the cache (deleting cookies, Internet files, and history) on your local workstation does not solve the problem, your network may be using a proxy server. Ask your network administrator to clear the cache on the proxy server, and the problem should be resolved.

Note: Close the browser and relaunch Activity

Other Considerations

For a complete list of supported and tested network and workstation configurations please see the link below to review all network and workstation configuration requirements:

PLE System Requirements

System Requirements Supplement

Chromebook Compatibility


How to get more help

Copyright Information

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