Hi, I just started using Horizon a week ago but now when I try launching it all it gives me is “Failed to connect to the server!” message. I’ve uninstalled it and reinstalled it 6 times already today, and I need to know why it won’t work for me? All the other links that the support sends me aren’t there anymore. I need some help understanding on how I can fix it. I even had my firewalls disabled and it still wouldn’t connect. I’ve already ran Horizon as Admin and reinstalling as an Admin but it still won’t connect nor will it go on offline mode. Any help would be great, thanks 
Something on your end is blocking Horizon from connecting to your Internet. Do you have any anti-malware or anti-virus software installed? If you do you need to set up an exception for Horizon in those too.
If you already did the above, try disabling your internet and running Horizon to see whether that works. If you are able to get it to run after disabling your internet, try again.
Also just to make sure, you have .NET framework 3.5 and the Microsoft C++ Redistribution 2010/12/15 packs installed correct?
Your last resort would be to follow these steps - Error message upon trying to open
I have a Windows 10 laptop so the C++ is up to date and the .Net framework 3.5 I have installed but it won’t work at all. I’ve already ruined my laptop anyways by restarting it completely, but it failed to restart n now it began to stay on the DELL logo screen that normally pops up when I try to sign-in to my laptop. So I’m kinda stuck now. Thank you for the advice though, I really appriciate it.
I’ve also already did the exception on Horizon on my antivirus and tried offline mode but none seem to work.
Is there an option in properties when you right click Horizon that says unblock? Also did you try the steps in the link I posted? That helps with most Windows 10 users for some reason.