Do you have another memory card?
Try swapping the card. Error 70 means the camera has a problem either capturing the image OR recording the image. If the problem is merely with recording the image then it could be a problem with the memory card. Unfortunately it can also be something else -- but the memory card is an easy thing to check.
You will need to eject and re-insert the battery (even if the camera is "off" do this step anyway.) The camera's power swtich technically does not deprive the camera of power... it is a "software" swtich and really just puts the camera into a mostly powered-down mode. Only eject and re-inserting the battery will force the camera to restart correctly.
If this does not resolve the issue, then the camera will almost certainly need to be sent in for service.
Note that Canon has a "loyalty program" and that Canon will let you trade in your old camera body for a newer body if it comes to that. You have to ask service about the program (the upgrades being offered change all the time and they don't publish the program anywhere.)
Tim Campbell
5D III, 5D IV, 60Da
