回复：大家请帮忙看看我们该怎么办

Go to do fingerprints as soon as possible. The application support center should allow you to so even your appointments are expired (Just be polite to explain your situation. I walked in and did my fingerprints a week before the appointment date - no problem).

In the meantime, write a letter to USCIS to explain what happened. Also you can call USCIS by POJ method to explain to an IO.

Even you case is closed b/c of this, you can reopen later - so don't worry too much.