I tried the reset by unplugging the system from the wall and the press the power button for 30 seconds.

but it didn't work at all.

That indicates a BIOS Recovery Image not found. You can try powering down the entire PC then boot it again but inasmuch as this is a new system I would suggest calling Dell tech support and give them the diagnostic code. They may have to arrange service for the system.

You can try a reset by unplugging the system from the wall and press and hold the power button for 30 seconds. Then reconnect the system to the wall receptacle.

Try clear cmos settings 

1. Remove the side cover.
2. Disconnect the battery cable from the system board.
3. Remove the coin-cell battery.
4. Wait for one minute.
5. Replace the coin-cell battery.
6. Connect the battery cable to the system board.
7. Replace the side cover.

Thank you, I just tried coin-cell battery pull off for 5mins and pull in, but it didn't work.

I only have one coin cell as I have only one computer, can't replace it.

Given it is a fairly new model the battery ought to be good. No indication to replace it. I think it is possible that the 7000 new from factory was doing an auto Windows and firmware update which failed and could not recover bios. You really should return it to Dell for repair or replacement.

Yes, that is reasonable.

I have already replaced with new one , just this is, but it only works for 3 days.

Old one happened after updating windows,  it only worked for one day, seems like I should return this for replacement again.

Thanks.