1] I tried with two cards, one 4GB class2 card and 32GB class10 UHS-I card. Both cards were working fine before I messed up. (Scroll down to see what I did)
2] Both cards work fine on other phones (Lumia720, lenovo P780) and in my laptop when I connect them using card reader.
3] Other cards work fine in my phone. (Cards from Lumia720, lenovo P780)
4] Phone detects above memory cards (4GB, class2 card, 32GB class10 UHS-I) in Recovery menu. (I browsed it when I was trying to "install zip from sd card". And I could browse the entire sd card with no problem.)
5] In ES File explorer it says "SD card unmounted or not present". In "SD & phone storage", it says "Total space: unavailable", "Available Space: Unavailable". In camera app, it says "Please insert an SD card".
6] "fastboot oem enableqxdm 0" is not working.
Here's what I did:
Everything was going smoothly.
1] 4GB card was in the phone, I did hard factory reset without unmounting the card. When I rebooted, above error occurred (SD card unmounted or not present).
2] I bought a new 32GB card, it was working fine in the phone.
3] While 32 GB card was inside phone: I installed "Superuser-3.0.7-efgh-signed" using "install zip from sd card" menu in "recovery" mode. When I rebooted above error occurred (For 32GB card).
4] I inserted previous 4GB card, it got detected and was working fine.
5] I did hard factory reset without unmounting the 4GB card. When I rebooted, above error occurred (with 4GB card).
Now both cards have above problem (SD card unmounted or not present).
Very strange problem. Will be glad to hear solution.
Thanx well in advance.