It looks like I’ve had the same issue as many of you, a Sandisk (in my case) SD memory card that goes from functioning perfectly, to only having a capacity of 30mb, and seen as having a RAW format. I’d taken 3 days of videos / photography on holiday, when the card seemed to be blanked and in the state above.
Reading through this thread and others, there’s lots of advice on how to format the card so that it will work again - but I think many people like me only want to restore the files, and would never want to trust even a repaired version of the card again to store anything of any value.
Fundamentally, I downloaded all the data recovery repair services (EaseUS Data Recovery, M3 Data Recovery, WonderRestore, Stellar Data Recovery etc). None of these found any data whatsoever. Partition software would not find a single partition, even on deep scan / full modes. I’ve read that partition software does not necessarily delete data, so my next step was to try to create correct partitions on the card, and hope this would allow me to scrape for some of the data with some of the above recovery apps. Next step was GParted (Mac Partition software you need to run in a VM Virtual box on Windows), as there is an account from someone that just mounting the SD card with this (without carrying out any functions brought back the data).
…I didn’t need to, repeatedly inserting and removing (without safely removing for brevity) the card eventually had all the data flash up again. I wasn’t able to copy much off it before it was derecognised and looked RAW to the PC again, but just repeatedly inserting and removing eventually brought up the system, and over a day or so, it stayed stable long enough to remove the data I needed. In total I tried inserting and reinsterting about 150 times. With breaks. It would seem to work best when it had been some time between attempts, but it may just have been random.
So to recover data, none of the official or freeware apps did anything, but perseverence had the card show that everything was in fact intact, but for some reason was unable to be accessed. Just try mounting on different devices, repeatedly, and hopefully you will get headway somewhere. Someone above posted an external SD card mounter as solving the problem (on Amazon), maybe that worked for them for a similar reason.
Good luck but I wouldn’t waste your time on data recovery apps if it’s showing as 30mb capacity. Strangely the SD card is becoming more stable over time, from seemingly being blank blank blank, three days ago (and showing nothing dozens and dozens of times), now it seems to load 20% of the time I plug it in.
Hope this helps some of you!