Insufficient storage space & Insert SD card

I’m using a Meizu M6, and a newly bought Sandisk Ultra micro SD XC 64gb.
Internal storage is about 1.67 gb free out of 16gb.

For the record, I have already checked the wiki tags and similar topics, as well as format, remount, cache clear, and/or reboot, but none of them worked.

So my phone and desktop can detect my SD, but:

  1. everytime I tried to create an empty, new folder on my SD, it gave me the “insufficient storage space” message… despite being empty as a clean slate.

  2. everytime I tried to use the camera, it gave me the “insert SD card” message… despite being able to detect it earlier.

Yet I can create new folders and move items to my SD if I connect it to my PC with some card reader.

What might caused this? Any pointers?