If you are using Firefox to run the ECS Agent or Supervisor clients, you will first need to install ClickOnce for Firefox.
2.Within Get Add-ons, search for ClickOnce
3. Click on the Install button next to FxClickOnce
4. Once installed, you will need to restart Firefox. Select Restart Now.
5. When opening any ECS client, you will select ClickOnce Install to open.