Sorry but it sounds like you've joined the 70D failed PCB / mainboard club.
Bay Area - CA
~R5 C (22.214.171.124) ~RF Trinity, ~RF 100 Macro, ~RF 100~400, ~RF 100~500, +RF 1.4x TC, +Canon Control Ring, BG-R10~DxO PhotoLab Elite ~DaVinci Resolve ~Windows11 Pro ~ImageClass MF644Cdw ~Pixel6 ~CarePaks Are Worth It
You mention that the <INFO.> button works on your camera, what happens when you press it? I ask because toggling that button will go through a cycle where certain information is displayed, taken away, hidden or disabled as that button gets pressed. One of the cycles it lands on will actually turn it all the way off, so we're wondering if perhaps that happened here.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.