I inserted an SD card from a dashcam because it was full. The first time I inserted the card, it showed up and I deleted all the files on it. I went to plug it back in the dashcam and it still showed "storage full". I plugged it back into my Mac and it will not show up anymore. Not sure what's going on here.
This may vary by dash cam. With my dash cam, you must not delete files on the SD card using Finder or some other operating system utility.
The dash cam is intended to manage its own storage and, by itself, will remove old video when full keeping just the most recent.
If there is a need to reinitialise the SD card, this has to be done with the utility provided for the dash cam.
In your case, I think you have corrupted the storage and need to reinitialise the SD card in the way required by the dash cam.