when I would try to get it to the MTR mode as per the directions you sent me, it would say NOSONG when I would try to get it into a Stereo or Mono track. which had me really confused at that point.
Had you created a song? The BR-80 doesn't create a new song when you initialize the card, as the Micro BR and others do. You have to create the song yourself. See page 57 of the BR-80 manual. If you haven't created a song, you'll get the "No song!" error message. TonyW had trouble with that when he first got his BR-80 because he assumed that initialization would create the song for him as it always did on his Micro BR. Perhaps you made the same assumption?
You said in the other topic that you were able to import the WAV file when you used the card that came with the BR-80. Since that card comes with a demo song already on it, that would explain why it worked. If you initialized that card and didn't create a new song, you'd have the same problem because initialization would erase everything from the card, including the demo song. Since the card would then have no songs on it, trying to import the WAV file would give you the "No song!" error message.
Try putting in the SanDisk card and creating a new song as per page 57. Then try importing the WAV file. If it works, then I suspect that there's nothing wrong with your SanDisk card. You just weren't aware that a song doesn't exist in MTR mode until you create it yourself.