Bill has a few XC MicroSD cards, but he can't seem to get his computer to write to them. Leo says that it's possible that Bill's computer can't support the size of those SD cards. The cards are formatted in XFAT and that may be different than what Bill's computer can handle.
If Bill has a current model computer, then it should be able to utilize those MicroSD cards. Bill could reformat them to NTFS, but that would make them non-compliant. Leo has a hunch that it's Bill's card reader that's causing the problem. He should check the specs of his reader to be sure it will support a 1TB XC SD card. If it does, then it's possible that Bill got burned with bogus or counterfeit cards. So that's something to pay attention to. Always get cards from a reputable source.