I use a Canon 50D with the Magic Lantern Firmware to take my videos.
One day it was working, the next it wasn’t.

It would power up.
The top LCD showed information.
When you pushed the shutter button, the lens would focus – but not take a picture.
The rear LCD wasn’t working either.

I found a number of post about how to fix such a problem.
Remove batteries, leave and then try again.
Which I did.
Still didn’t work.
So I left it, on the side, all ready to have to buy another.

Then, today, I happened to pick it up and try it.
It worked!
Took photos, rear screen displaying – I was one happy bunny.

Then I noticed it didn’t have a CF Card in it.
Which seemed strange, as it was set not to take photos without a card.
Back in went the 64GB card I use.
Hit the shutter button – nothing.

Then I remember reading on one webpage about damaged CF Cards.
This seemed unlikely.
In went my other, 16GB card.
Nothing.

Then I wondered, could it possible be?
I formatted the 64GB card on my Mac.
Left the battery out for an hour.
Put back the card…
Pushed the Shutter Button…
It worked!

So what was the problem, I hear you ask.
A while back I had to rescue some deleted photos from the 64GB card.
Using recovery software on my Mac I managed to save all the deleted photos.
Which means it appears that something about the recovery process altered the card.
In such a way it didn’t allow the camera to work.
However, the hard reset did work, putting the default setting of shoot without card active.

Time to put back Magic Lantern,
Finish setting up my “shoot at home during C19” studio,
And start documenting all the bat crazy shit that has been my C19 experience.