It's definitely not that it's too large - they don't make SD cards that would be too large yet (and won't be for a while). Put it into a PC and see if it's "supported". If it is, format it (as FAT32 if it's up to 32GB, as exFAT if it's larger). Then the phone should accept it. (But format it in the phone - there's a slight difference.)
If the PC doesn't accept it, the card is probably bad. Then it depends on whose card it is, and where you bought it. If it's a cheap Chinese card, toss it. If it's a SanDisk, go to
SanDisk microSD Tech Support, upper right for live chat. If it's anyone else's, you're on your own contacting the vendor. ("Vendor" because only SanDisk and Samsung make the chips, everyone else just packages them and sells them.)
