My creations and collections are not affected, but neither my owned nor installed games appear in the library. Luckily, I haven't purchased anything over itch.io yet, it's just been game jam games, but I can see this being a problem if it's a glitch.
Maybe it just hasn't finished scanning? I do have a lot of folders on my computer, but it's been scanning for a good 10 minutes already. Clicking view all on either category just leads to the "nothing to see here" page.
v23 kept information about "installed games" in another location, in a different format.
v25 attempts to scan that, and update the information from the itch.io API. If the game can't be found, or the upload is gone - it won't show up in your library again.
I know that's unfortunate, and it's also why v25 stores install information directly in the installed game's folder. That way you can move around your games, reinstall your OS, change computers entirely, and import them afterwards with no problem.
edit: If you navigate to your install location from within the app, and use the "Scan locations for games", button on top you'll:
