You need to format the disk in drive E: before you can use it. Nine times in ten that sentence is reporting a broken index rather than an empty card. A memory card holds two separate things: your photographs, written across the flash in a long sequence, and a small table at the front recording where each file begins and ends. Damage that table and the camera can no longer list anything, so it offers the only repair it knows how to offer. The pictures themselves have not shifted a byte.
The table breaks for dull, mechanical reasons. A card pulled while the write light was still on. A battery that died mid-burst. A card used in two bodies with different firmware. A counterfeit card claiming a capacity the flash inside cannot actually deliver, which works fine until you cross the real limit and then loses everything past it. And plain wear, because flash cells have a finite number of write cycles and a card that has taken four winters of wildlife work has used a great many of them.
SanDisk turns up more than anything else on this bench, for the obvious reason that it outsells everything else. Extreme and Extreme Pro cards are what most working photographers up here are shooting on, and they are good cards. But volume means volume, and there are a few SanDisk-specific things worth knowing.
First: SanDisk's own utilities are not recovery tools. The SD Memory Card Formatter and any manufacturer format routine will do precisely what the name says, and doing it to a corrupted card overwrites the very structures a recovery works from. RescuePRO, which ships with some cards, is a file-carving tool aimed at healthy cards with deleted files; pointed at a failing card it simply keeps a dying controller running. Second: counterfeit SanDisk cards are everywhere, and a fake Extreme Pro bought cheaply online is the single most common cause of a card that corrupts a shoot for no apparent reason. Third: when a SanDisk card dies outright — no detection anywhere, on any reader — the failure is usually the controller rather than the memory, and the memory can be read directly past it. That is a bench job, not a software one, but it is a real route back and it works on cards that every computer in the house has already refused.
Do these, in this order, then stop. Get the card out of the camera and read it through a decent standalone reader instead of through the camera body, because the camera's own file handling is a layer of interpretation you do not want in the way. Try a second reader and a second computer. On a full-size SD card, check the small write-protect slider has not been knocked downward, which is a genuinely common and entirely harmless reason for a card that looks broken. Inspect the contacts for corrosion or a bent pin, and the plastic for a hairline crack by the notch.
Then stop. Do not format. Do not run chkdsk or scan-and-fix. Do not let the camera repair the card, and do not shoot another frame on it — every new photograph is written into the space the old ones are sitting in. If Windows offers to fix errors, decline. If macOS offers to initialise, decline. The card is still readable at a level below the file system, and that is where a recovery works from. Every repair tool operates above it and writes as it goes.
A card that refuses to format has usually gone into a hardware read-only state, which is the flash controller protecting itself once it can no longer manage the wear-levelling behind the scenes. It sounds terminal and it is often the opposite: a card locked read-only can still be imaged, and an image is all a recovery needs. The other cause is a failing controller, where the card enumerates briefly and then disappears, or is not seen at all. That one is read at chip level, past the controller entirely.
Either way the method is the same. The card is imaged sector by sector, read-only, with nothing written back to it. The file system is rebuilt from that image where its records survive. Where they do not, the photographs are carved out by their content signatures — RAW files, JPEGs and video all have recognisable headers — and the results are opened and rendered before anybody claims a recovery, because a file that has a name and a size but will not display is not a recovered photograph. Fragmented video is the hard case and it is worth being honest about that; stills come back far more reliably than long clips.
A large share of the card work coming into this bench is from photographers, and the north-east gives them a specific set of problems. Cards swapped with cold hands on a hill in the Cairngorms get pushed in askew and the contacts suffer. Condensation forms when you go from minus five outside to a heated car, and it forms inside the camera as well as on the lens. Salt spray along the coast at Fowlsheugh or Troup Head gets everywhere, and a card that has been in a bag on a boat has had a harder life than it looks.
None of that is an argument for expensive cards so much as an argument for habit. Format in the camera rather than the computer, and do it before a shoot rather than after. Do not fill a card to the last frame. Retire cards on a schedule instead of waiting for them to fail, because they always fail on the day that matters. And copy off at the end of each day even when you are tired, because the shoot you cannot repeat is the one you will lose. If a card has already gone, the diagnostic here costs nothing and is finished within 2 working days of arrival, and you get one fixed written figure before anyone touches it.
Hold one line and the shoot usually survives. The prompt is reporting a broken index; the photographs sit untouched behind it. They stay recoverable right up until a format, a repair tool or a fresh frame writes over them. Eject the card, put it in its case, and leave it alone until it can be imaged properly.
Diagnosis costs nothing and takes 2 working days from arrival, the figure is fixed in writing, and logical work runs no fix no fee. Begin online, or lift the phone.