In case it doesn't, then it may be an issue with the memory card causing the camera to not power on. Turn the camera back on to see if it does power on. If the camera does power on, then let's turn off the camera and insert the memory card only. Turn on the camera body only to see if it powers on. Make sure there are no other accessories attached to the camera body. With the camera switched to the 'Off' position please remove the lens and the memory card from the camera. You may use a dry microfiber cleaning cloth to wipe the contacts. Please check for debris inside the battery compartment where the pins are located and check for debris on the metal contacts on the battery pack.

We would recommend to use an official Canon battery pack in case you are using a third party battery and please use the official Canon charger when charging the battery. I understand you have performed a few troubleshooting steps but let's see if the following will allow for the camera to power back on.

I'm sorry to hear that your EOS 7D is not powering on after attempting to update its firmware.

Canon 7d firmware latest