Hello MoonChild711,
Thanks for reaching out using Apple Support Communities!
We understand you're having an issue with the SD card or adapter; we're happy to assist you.
To learn more, has this adapter and card worked without issue in the past? Does any software need to be installed or updated in order to the SD card or adapter to work properly with your Mac? Some adapters or cards require additional software to be installed.
Do you have another adapter you can test with?
This Apple Support page might have some helpful steps to resolve the issue as well: Import photos using Apple camera adapters
Cheers!