WordPress Upgrade – API files returning 404 on Multisite

The error was caused by a rewrite rule in our web.config file:

<rule name="API" stopProcessing="true">
    <match url="API" />
    <conditions logicalGrouping="MatchAll" trackAllCaptures="false" />
</rule>

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)