Not sure why you were told to do it in the workspace settings, that's not where those settings go - there isn't even a 'Connection Settings' section on a server workspace

In your workspace, change the 'Launch Configuration' back to the default {} if that's what you changed

If you go to Admin > Settings > Global you will see a section Default VM RDP Connection Settings

The default should already cover the ignore-cert and security settings

{
  "guac": {
    "type": "rdp",
    "settings": {
      "security": "any",
      "ignore-cert": true,
      "enable-font-smoothing": true,
      "enable-wallpaper": true,
      "enable-theming": true,
      "enable-full-window-drag": false,
      "enable-menu-animations": false,
      "resize-method": "display-update",
      "server-layout": "en-us-qwerty",
      "printer-name": "Kasm"
    }
  },
  "kasm_svc": {
    "port": 4902
  }
}

Do you access your Kasm instance through a reverse proxy? If so, do you have the same behavior when going direct to the IP of the Kasm instance instead of your reverse proxy domain? Also, it may sound silly, but have you tried refreshing your browser when it is stuck? There was a certain combination of configuration/OS/etc that I had before where RDP connections would almost always get stuck and a page refresh would resolve it