You haven't listed the model of your phone so I am going to take a shot in the dark here. Most phones will format the card on their own so it could be that the phone in question doesn't support SDHC, you might try an older MicroSD (not SDHC) card and see if it works.
Answers & Comments
You haven't listed the model of your phone so I am going to take a shot in the dark here. Most phones will format the card on their own so it could be that the phone in question doesn't support SDHC, you might try an older MicroSD (not SDHC) card and see if it works.