Preliminarily, The only app that was able to read my original SD card was through the Storage in Settings. I could read and write to the card. No other apps were able to access the data on the card. It seems almost as if it were encrypted or just invisible. I then inserter a different 16 GB SD card, which the phone identified as a New Card. I set it up for use, and it read the content on the card without issues.
I reformatted my original 64GB SD card on the phone. It created the necessary directories. I removed and reinserted the SD card on the phone. I identified it as a New Card, and I set it up. I was then able to access the card without further problems using ES File Manager. I inserted the SD card back into the Surface Pro 4 and transferred my data back onto it. The transfer process is slow due to lots of data on the card, but I will post an update when it finishes.
I hope this helps others get their phones working.