Greetings, Mark-A27
I'm sorry to hear that your EOS 7D is not powering on after attempting to update its firmware. 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.
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. 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. You may use a dry microfiber cleaning cloth to wipe the contacts.
With the camera switched to the 'Off' position please remove the lens and the memory card from the camera. Make sure there are no other accessories attached to the camera body. Turn on the camera body only to see if it powers on. If the camera does power on, then let's turn off the camera and insert the memory card only. Turn the camera back on to see if it does power on. In case it doesn't, then it may be an issue with the memory card causing the camera to not power on. I would suggest testing a different memory card.
If the camera does turn on with the memory card, then let's turn off the camera and mount the lens back on to see if this is what is causing the power issue. If the camera does not turn on, then I would suggest testing a different lens on the camera. If other lenses work, then it may be an issue with the current lens you're trying to use.
In case the EOS 7D is still not powering on then we would have recommended to send it in to our facility for service but I'm sorry to say that the facility no longer repairs this model. An alternative option would be to participate in the Canon Upgrade Program.
The Canon Upgrade Program option allows you to replace your current camera with a new or refurbished Canon camera at a discounted price. If you would like to take part in the Canon Upgrade Program, please call our Sales Department at 1-866-443-8002 from Monday - Saturday between 9:00 am to 9:00 pm ET. Let them know you have been working with email technical support and the Canon Upgrade Program was offered. Be sure to have your serial number for your camera available at the time of your call.
