<p>If you have found this page looking for a solution for the <strong><em>Event ID 31 Windows Update failed to download an update</em> error</strong> log then you came to the right place.</p>
<p>The probable cause of this error lies (at least in our case) in the missing mime-type on the IIS server.</p>
<p>To fix this issue, log in to your WSUS server an open IIS administration console.</p>
<p>From the left pane expand the <strong>Sites</strong> link and click on <strong>WSUS Administration</strong>. In the right pane double-click on the <strong>mime-types icon</strong> as you can see from the image below.</p>
<p><img class="alignnone wp-image-3869 size-full" title="Event ID 31 Windows Update failed to download an update" src="https://www.wincert.net/wp-content/uploads/2020/08/mime-types.png" alt="Event ID 31 Windows Update failed to download an update" width="1034" height="370" /></p>
<p>From the right <strong>Actions</strong> pane click on <strong>Add</strong> to add the <strong>new mime-type. </strong></p>
<p>In the <strong>File Name extension field type .msu</strong> and in the <strong>mime-type field</strong> <strong>type application/octet-stream</strong></p>
<p><img class="alignnone size-full wp-image-3870" src="https://www.wincert.net/wp-content/uploads/2020/08/wsus-add.png" alt="" width="642" height="293" /></p>
<p>Click <strong>OK</strong> and restart WSUS client for the changes to take effect. You should not receive <strong>Event ID 31 Windows Update failed to download an update</strong> error logs anymore.</p>
<p><img class="alignnone size-full wp-image-3871" src="https://www.wincert.net/wp-content/uploads/2020/08/windows-update-error-2.png" alt="" width="577" height="385" /></p>
<p>Hope this helps.</p>

Event ID 31 Windows Update failed to download an update
