Samsung Galaxy Core Prime doesn't detect micro SD card

Hi, I desperately need space on my phone, so I got a SanDisk 8gb micro SD card. After inserting it, my phone doesn't react at all and I can't mount it, like it's not even there.

I tested it in a tablet - worked - and then my sister's phone, which is the same model. It worked fine there too.

Is there anything I can do to use it in my phone? The card fits snugly, so I know it's in properly, and I used compressed air to clean out the slot. Anything else I can try? Thanks in advance!

EDIT: First time posting from mobile, how do I flair my post? Sorry for the trouble.