If you are running a version of Horizon earlier than 7.10 please read this blog

[chrisdhalstead]

If you are running a version of Horizon earlier than 7.10 please read this blog regarding Adobe Flash end of life.  You will not be able to just stop updating a browser and continue to use Flash.  

https://techzone.vmware.com/blog/adobe-flash-player-end-life-and-vmware-horizon