I have tried looking through other solutions for my problem and they seem to not work.
My error code is 0x80070643 - Fatal error during installation
And it says I am missing “setup.msi” when I try to install it. I am on Windows 10 so I have all programs needed to run horizon.
Do you have .net framework 3.5 installed? You need 3.5, 4+ does not include it and it will not work without having that installed. The missing MSI means the folder/file is being deleted when it is unpacked.
Could be AV because I had a similar issue when I was re-installing after updating to win 10
I have windows 10 so it has it from factory settings ( .net framework 4.5 ) and my AV is fully disabled…
.Net Framework 4.5 does not include 3.5 which is required for Horizon.
Oh. Ill try uninstalling 4.5 and using 3.5
Don’t uninstall 4.5 just install 3.5 also. I have like 2-4.6 installed on mine.
Ok
Weird… I have .net framework 3.5 now but it still says the same error…
and missing “setup.msi”
( Restarted PC after installation of .net framework )
Have you tried re downloading the installer after disabling your AV
Yes and it still does the same thing
Could you help me when ever I try to run Horizon it alerts me that I can’t connect to the server and then puts me in offline mode which doesn’t have that many mods available. Please Help!!! 
There’s a search button feature on this website, it’s the magnifying glass symbol thing.
Try entering some keywords there.
Hope I’ve helped