Pages stored only in iCloud Drive or Google Drive need to download before they can open.
Showspaces in iCloud Drive or Google Drive work like local folders. To save disk space, those services may keep a file in the cloud until you open it.
The app checks whether the file is on your Mac. If it needs downloading, the page shows as waiting and the app offers to fetch it.
In the Gallery, such a page shows its thumbnail if one of your Macs has drawn it. If none has, lite.computer makes one: it downloads the page, draws it, and returns it to the cloud. See Gallery View.
How long a fetch takes depends on the size of the file and the speed of your connection. It is the same wait as downloading it in Finder.
Some people choose to keep a Showspace on their Mac so pages open faster. If a Showspace matters enough that you never want to wait, pin it. In Finder, right-click the folder in iCloud Drive and choose Keep Downloaded. Google Drive has the same idea in its offline access setting. The pages then stay on your disk and open instantly, at the cost of the space they take.
An agent writing into a synced folder writes locally, and the service uploads afterwards. If you are watching the same Showspace on a second Mac, the page appears there when the sync reaches it. That upload needs the Mac to stay awake. A MacBook that goes to sleep on battery, or with its lid closed, holds the page until it wakes again.
Still stuck? Write to support@lite.computer.