Meaning it’s dead, won’t boot, and no online access?
Do in reverse order to what you originally did. Reverse all steps.
Try to restart the bios by removing the battery. Or a button if this model has one.
https://www.qnap.com/en/how-to/faq/article/the-different-ways-of-resetting-your-nas-explained
https://www.qnap.com/en/how-to/faq/article/my-nas-cant-be-powered-on-or-it-does-not-boot-how-to-fix-it
https://wiki.qnap.com/wiki/Firmware_Recovery
At worst, you could have damaged your motherboard…
Problem #1: The NAS does not power on.
Possible cause: Faulty power adapter or power supply
Check if the LEDs on the front panel turn on after pressing the power button.If none of the LEDs turn on, the power adapter or power supply of your NAS may be faulty. You can try plugging in the NAS to another power outlet to double-check.
Solution: Contact our Service Portal or your QNAP reseller for warranty repair service. For out-of-warranty units, a replacement power adapter/power supply can be purchased from the QNAP accessories store.
Problem #2: The NAS does not pass the POST (Power-On Self-Test).
Does the NAS produce a short beep about 5 to 10 seconds after being powered on? If not, the system has failed to pass the POST. The most common causes of this are a faulty motherboard or faulty RAM.
Solution: Contact our Service Portal or your QNAP reseller for warranty repair service.
Problem #3: Corrupted firmware image
Within five minutes after powering on your NAS, you should hear a long beep (about 1.5 seconds long). This indicates that the QTS operating system has finished booting.
The absence of a long beep may indicate that your NAS has corrupted firmware. This results in the NAS being unable to boot QTS.
This could be caused by the NAS being abruptly powered off during a firmware update.
Solution: Follow the firmware recovery procedure that is documented step-by-step in this guide. If recovering the firmware does not solve the issue, contact our Service Portal for assistance.
Boot up the NAS without drives installed.
If NAS is not able to boot up without drives installed, and no long beep sound after 2-4 minutes, this means the firmware on the DOM has failed. You may try the firmware recovery from the link below (note that not all NAS models have the recovery process available): Firmware Recovery Guide