WordPress MultiSite 404 on Admin Dashboard

If you are experiencing a 404 when switching to the dashboard of a given site, verify the web.config is accurate. We've found that older versions of WordPress have incorrect rules within web.config. Try the following web.config:

 <?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
<rewrite>
<rules>
  <rule name="WordPress Rule 1" stopProcessing="true">
     <match url="^index\.php$" ignoreCase="false" />
     <action type="None" />
  </rule>
  <rule name="WordPress Rule 2" stopProcessing="true">
     <match url="^([_0-9a-zA-Z-]+/)?wp-admin$" ignoreCase="false" />
     <action type="Redirect" url="{R:1}wp-admin/" redirectType="Permanent" />
  </rule>
  <rule name="WordPress Rule 3" stopProcessing="true">
     <match url="^" ignoreCase="false" />
     <conditions logicalGrouping="MatchAny">
        <add input="{REQUEST_FILENAME}" matchType="IsFile" ignoreCase="false" />
        <add input="{REQUEST_FILENAME}" matchType="IsDirectory" ignoreCase="false" />
     </conditions>
     <action type="None" />
  </rule>
  <rule name="WordPress Rule 4" stopProcessing="true">
     <match url="^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*)" ignoreCase="false" />
     <action type="Rewrite" url=" {R:2} " />
   </rule>
   <rule name="WordPress Rule 5" stopProcessing="true">
     <match url=" ^([_0-9a-zA-Z-]+/)?(.*\.php)$ " ignoreCase="false" />
     <action type="Rewrite" url="{R:2}" />
   </rule>
   <rule name="WordPress Rule 6" stopProcessing="true">
     <match url="." ignoreCase="false" />
     <action type="Rewrite" url="index.php" />
   </rule>
</rules>
</rewrite>
</system.webServer>
</configuration>