Thanks for confirming your setup.

Does your portal look similar to the below? If so, this is Workspace One.

Have you tried uninstalling the installed Horizon Client from Chrome OS and then re-authenticate to the portal to see if it triggers a subsequent installation of the Horizon client? I'm wondering if the association with the browser is simply broken and a forced install from within the portal (if it prompts you) will rectify the problem.  The only other solution I can think of is to try and use a different browser on the Chrome device and see if that works (firefox for example) - which would eliminate the problem at the remote end and highlight the issue is with the Chrome Browser itself on the device.

If this doesn't solve things and it is indeed a Workspace One portal as per the image above, I would suggest moving this post over to the Workspace One forum as it is less of a Horizon issue, more of a portal integration problem.