Big-IP LTM - VMware View - HTTP Error 404 - Object not found

Couple troubleshooting thoughts:

Try accessing the virtual server address to see if you have a response (you will have cert warnings, but this is just a connection test). If you have a response, then verify your DNS is setup correctly. If you do not see a response then verify ports 443/4172 are available from the horizon client to the BIG-IP virtual server address. Tcpdump/capture would be useful on the big-ip/client to verify connection requests are making it to the BIG-IP. If the request is making it to the BIG-IP VS address, then check out the server side also using tcpdump/capture to verify the horizon client request was properly proxied to server. You should see the server response going back to the big-ip, if not then verify the virtual servers snat setting is setup correctly. If your servers are not using the big-ip as a gateway, then you should have snat setup to automap or pool. If you are using automap, verify you have a self-ip address on the network in which the pool members reside. If using a pool, then verify the ip address pool is on the same network as your pool members.