Connecting RDP through Fortigate

Hey guys, I recently got my hands on an older model Fortigate 80C. I've set up a test environment with 1 server and 2 PC, with the Server and PC 1 separated from the network through the Fortigate.

i've setup fortigate according to this video: https://www.youtube.com/watch?v=pSyrM_rGUY0

Basically I created 2 policies that allows all traffic and services from Internal to WAN, and from WAN to Internal.

I also route it through the default gateway so I can access the internet.

Problem now is I can't access the Server using PC 2 anymore(Still able using PC 1). My server is under a domain, let's use "Resident.local" to represent it for now, and "Resident" to represent the server name.

On the Remote Desktop connection, this is how I input:

Computer: Resident:3389

Username: Resident.local\Administrator

I've also set the RD gateway server settings to use the domain: Resident.local

Also checked Use My RD Gateway Credentials.

I get the error message: The remote resource can't be reached.

This is even after I entered the correct username and password when prompted.

I'd like to know if there are any additional settings that I need to tweak on the fortigate interface. Thanks all!