Here are the most common things people look for with specific RimWorld versions: 1. Missing Executable or Runtime Files
If the .zip file is missing a "piece" to make it run (like a .dll or the RimWorldWin64.exe ), it’s usually because an antivirus program flagged and quarantined it. RimWorld.v1.4.3580.zip
If you are playing offline, many modders keep "Legacy" branches of their mods specifically for 1.4. 3. Updating to the Latest 1.4 (or 1.5) Here are the most common things people look