The issue may be that the laptop hasn't been able to upload the file to iCloud after you make changes. It takes a little time for iCloud to sync the file. If the laptop is quickly shut down or if it is on battery and the lid is closed it may not have time to write the changed file up to iCloud. That's my guess...
QuickBooks wasn't designed originally with iCloud in mind of course. One of the side effects of that is QB will write out information to the file whenever it wants. So even opening the file will cause some changes to be made (like updating the date, etc). This means when you open it on the desktop you may have more recent changes on the desktop file than what is in iCloud from the work you did on the laptop. But in practice I find I just choose whichever file I last entered data in - that's the one you want. If you just got home and you were working at the office on the laptop choose the iCloud file.
The other thing we've seen since shipping is that sometimes people have multiple copies of QB open on a single machine. Usually its the QuickBooks Server and a QuickBooks client. That results in some confusing circumstances when sharing the file in iCloud. But if you aren't doing multiuser that probably isn't the case here.
