Hi,
Try to access RWA using browser other than IE, then, click to access your Windows Server Essentials, it will prompts you to download the .rdp file. Download it and using Notepad to open it. Find below section and edit it as below to enable multi monitors function:
use multimon:i:1
Save the change and using RDC(MSTSC) to open the .rdp file and establish remote desktop connection to your WSE.
More information about “use multimon:i:value”, you can reference article -> Supported Remote desktop RDP file settings:
https://learn.microsoft.com/en-us/windows-server/remote/remote-desktop-services/clients/rdp-files