Re: does android support external microSD cards
1) Since 4.3, the card is part of the file system, it's no longer free external storage, so an app can only write to a folder it has permission to write to. If an app creates a folder on the card, it can write to it. If some other app created it, or it was created before 4.3, you'll have to have the app create a folder, then move everything from the old folder to the new one (you can use a card reader in a PC - Windows doesn't know about Linux permissions).
2) if you want the old way back, you have to root the phone, then run
NextApp SDFix: KitKat Writable MicroSD (root). Then any app can write anywhere, including old folders.
3) A phone that can't read the card at all (assuming it's the same card as the other phone, so you know it's not a bad card) has a problem that needs to be fixed. If it's a different card, it could be a bad card. Put it into a card reader and see if a PC recognizes that there's a card being inserted. (Even if it can't read it.) Format the card (Right-click/format). If it fails, the card is bad. If it succeeds, put the card into the phone, restart to recovery and format the card. Restart normally and you should be able to use the card.
Note: If you have a bad SanDisk card, go to
SanDisk microSD Tech Support and start a live chat (upper right corner of the screen). Their cards are warrantied for 5 years.