Horizon isnt opening

Ive battled with this all download all day. Ive deleted all antivirus software, it told me that Horizon has stopped working and wouldn’t open. I downloaded the 3.5 software someone had suggested from another chat, and re-installed Horizon. Still the same thing. Some people have said that it will open when its not connected to the internet, but mine doesn’t. Is there something that I need to do extra, or something I haven’t done? Please, any help would be amazing.