GOG connect found two games I own on Steam but did not find two other games I own...

Is anybody else having this problem?

Give it time. It's very wonky. It always fails the first time for whatever reason... just refresh it every half hour or so. It's never failed to find everything for me... it's just weird how it takes several tries.

Try logging out and back in again. I remember reading that helped in some cases.

can someone here tell me what gog connect even does?
example… I have F.E.A.R. platinum on steam. can I download it here instead?

Try reading the numerous other posts on here about connect, or the lengthy text on the page itself. Object is a time limited special offer to gift a free copy of a game you own on steam, from a specific list of available titles to your library here. It is only a couple of games once in a while and has a fair few issues with expansion packs and what not. What is available is on the connect page, if there is nothing there then there is nothing to connect.