A game says it can't reach Steam

"Application load error 3:0000065432": the game needs Valve's "Steamworks SDK Redist". Turn on Steamworks for Windows games in Setup; Steam downloads it the next time it starts. Games on a second Steam library (an external drive) use the copy in your main library; versions before October 2026 didn't look there.
The game closes at once, or says Steam isn't running: make sure Steam is running and signed in, and that Setup shows Steam support as ready (use Update… if it offers one).