You may be asked to configure an existing VM to become a Session Host. There are detailed steps here:

https://learn.microsoft.com/en-us/azure/virtual-desktop/add-session-hosts-host-pool?tabs=portal%2Cgui&pivots=host-pool-standard


The link above also covers steps on how to do it from scratch (if you don't have a VM already created).


Generate a registration key:


1) Sign in to Azure Portal

2) Navigate to Azure Virtual Desktop

3) Select Host Pools and select the name of the Host Pool you wish to add a Session Host to.

4) In the overview section, click Registration Key

5) Generate a Registration Key, enter date/time (date/time not important, just set it to 1 day in the future)

6) Select download text file and keep it available.


1) Make sure the virtual machines that you want to use as session hosts are joined to Microsoft Entra ID or an Active Directory domain (Active Directory Domain Services or Microsoft Entra Domain Services).


2) If your virtual machines are running a Windows Server OS, you need to install the Remote Desktop Session Host role and then restart the virtual machine. For more information, see Install roles, role services, and features by using the Add Roles and Features Wizard.

# Quick Powershell commands to assist you in installing RDS
Get-WindowsFeature RDS-RD-Server

# Install RDS Session Host Role
Install-WindowsFeature RDS-RD-Server -IncludeAllSubFeature -IncludeManagementTools

# Essential to restart after that is done
Install-WindowsFeature RDS-RD-Server -IncludeAllSubFeature -IncludeManagementTools

# You will need to license this but you usually have a grace period upon install.


3) Sign into the Azure VM as an Administrator


4) Download the installation files for the Agent and the Agent Boot Loader by using the following links:
https://go.microsoft.com/fwlink/?linkid=2310011 (AVD Agent)

https://go.microsoft.com/fwlink/?linkid=2311028 (AVD Agent Bootloader)


5) Double-click the first MSI (ensure you do this one FIRST, it's really important)
Follow the installation steps, agreeing to T&C and you WILL be prompted to enter the registration key I told you to keep available. Copy and paste it into the placeholder (it will paste as a single line rather than a block) click next and complete the installation


6) Double-click the second MSI (Bootloader) and complete the installation.


7) Restart the server again and wait 5 minutes.


8) Go back to the Host Pool and click on Session Host and you should have 1 Session Host with Status: Available.


9) If your Session Host has a status of "Unavailable or Upgrade failed" you will need to do the below:
Restart the VM again
Ensure in appwiz.cpl you can see the highlighted:

All 4 of the above are REQUIRED for a session host to become "Available"

If the above is all correct then you will need to check event logs as each case is quite specific but if you've followed the guide correctly you shouldn't run into any issues.