Error using WebReport to call REST API for authenticating Content Server

Hello everyone,

I have this basic WebReport as follows:

[LL_WEBREPORT_EXCLUDEHTML /]

[LL_WEBREPORT_RESTCLIENT

@HOST:[LL_REPTAG_$host /]

@PORT:[LL_REPTAG_$port /]

@URI:/OTCS/cs.exe/api/v1/auth

@METHOD:POST

@TIMEOUT:10

@USERNAME:[LL_REPTAG_$username /]

@PASSWORD:[LL_REPTAG_$password /]

@OUTPUT:ASSOC:outputAssoc /]

[LL_REPTAG_!outputAssoc ASSOC:AuthAssoc /]

<br>

[LL_REPTAG_!outputAssoc /]

However, when I tried to run this web report, I got an error like so:

Does anyone have any idea? Thank you in advance!