I figured it out
Connect the phone (Mass Storage) with the SD in via USB and check if 2 partitions are recognized on the PC 1st (internal) and 2nd (SD-not accessible).
While connected to the PC take the cover off atrix and remove SD and slide it back it, if it doesn't see it instantly try again. The phone should say that it has detected the card. You might have to format it if it's not FAT32
No need to flash it again.
Hope this helps