I just updated my firmware to the most recent version today and since I did, I suddenly started getting "Invalid SD Card" on my DJI Go 4 screen. I thought I simply needed to format my SD card and did so. But I could not do so on the DJI app. I then successfully formated as ExFAT on my Mac and no success. I then repeated as FAT32 (no success).

I know that this not a card compatibility issue for two reasons - first, I flew and recorded 4K using this card without any hiccup yesterday and suddenly this happens after the firmware upgrade. Second, I am using a SanDisk Ultra PLUS UHS-1 SDHC card, which is an approved card. Unless the firmware changed something about the way the drone reads cards, something is amiss.

I also did some additional troubleshooting - I was able to use this MicroSD card successfully across other devices, including in a DJI Spark using the same app! Has anyone else had a similar issue and is aware of a workaround?

Do you still have the original SD card of the drone? Please try the original SD card,  besides,  when you are trying to format the SD card via the APP, what error message did you get? Is it 64G or 32G?

I'm using a SanDisk Class 3, 16 GB SD card. I have six other SD cards at home and every one of these give me the same message. None of these cards are greater than 16 GB. I understand you're trying to say that the SD cards are finicky but seriously these SD cards all worked in this drone 24 hrs ago!

Also, yes I did try the card that came with the drone. That didn't work either