Prism downloads update, but doesn't actually update

There is a known issue that may occur when updating Prism on Windows. You may experience this issue when updating Prism to a newer version using the software update feature. After clicking the "Install Update" button in the Software Update dialog, Prism downloads the update, then Prism quits and nothing happens.

This issue may occur with Prism versions 7.05-8.3.0 on Windows 10 with the security intelligence update of Windows Defender Antivirus from mid-January 2020. Note that we have not seen this issue on Windows 8 and older.

IMPORTANT: there is nothing wrong with Prism's update files. Updating from any Prism version worked fine until mid-January 2020, when Microsoft introduced a particular Security intelligence update for Windows Defender Antivirus. There were numerous Defender updates released in mid-January 2020. While it is unclear exactly which Defender update introduced the issue with Prism, we can confirm that the issue can be reproduced with Defender's security update 1.307.2308.0 released on 01/14/2020. Note that we have not seen this issue when using Defender's update 1.307.2269.0 (released on 01/13/2020) or older updates to Windows Defender.

This issue has been resolved in Prism 8.3.1. We urge you to update to this version of the software so that in the future you can seamlessly update to future versions of Prism.

There are several ways to update to Prism 8.3.1 if you are experiencing this issue:

Temporarily turn off Windows Defender before updating to Prism

1. Quit Prism
2. Turn off Windows Defender by following instructions here: https://support.microsoft.com/en-us/help/4027187/windows-10-turn-off-antivirus-protection-windows-security
3. Start Prism and perform the update
4. After Prism has been updated, be sure to turn Windows Defender on again

Download the Prism 8.3.1 installer directly

You can download the Prism 8.3.1 installer directly from the Updates page. After downloading the installer, run it to update Prism.

Install update from the downloaded file

If you have already clicked "Install Update" in Prism's Software Update dialog, Prism will have successfully downloaded the updater. However, due to the issue described on this page, it will have been blocked from launching by Windows Defender. You can find the file on your computer and manually run it. To do so:

1. Open the folder: "system disk:\Users\[user_name]\AppData\Local\Temp". Note that the AppData folder is hidden by default. To display hidden files and folders follow the instructions listed here: https://support.microsoft.com/en-us/help/14201/windows-show-hidden-files
2. Locate the file "webinstallprism8.exe"
3. Double click the file to run it