Hi,
Which version of IIS are you using? In case it is IIS 7, you would need to add following code into your web.config (<system.webServer> section) file
<security>
<requestFiltering>
<requestLimits maxAllowedContentLength="2147483648"/>
</requestFiltering>
</security>
The value of maxAllowedContentLength is in bits.
For more information please take a look into
documentation.
Best regards,
Ivana Tomanickova