SanDisk Ultra Fit 128 GB - Device not recognized

I purchased the  SanDisk Ultra Fit 128 GB to use on a Sylvania portable DVD player , as it has a USB port. I copied MPEG movies onto the flash drive and plugged it in… no problem. Great!

However, later I tried copying a 4+ GB MPEG file to the flash drive and was informed the file was “too large”. I checked online and was informed this was a limitation of exFAT, which led me to format the flash drive to NTFS (using “Default allocation size”). On completion I copied over the 4+ GB MPEG without issue. Great!

Then, when I plued the flash drive into the Sylvania’s USB port and switched over to it I was informed " Device not recognized". Huh. It would show any files on the USB drive. So I unplugged it, brought it back to my computer, re-formatted back to exFAT (using “Default allocation size”) and copied over a <4GB MPEG movie, one which had worked before, and brought it back to the Sylvania. Again it informed me: “Device not recognized”.

So, in essence, by formatting the SanDisk Ultra Fit I had somehow made it unreadable by the Sylvania. I even tried to reformat it by restoring default settings, but still nothing. Does anyone have any suggestions as to what I would need to do to fix this strange issue?

EDIT: While investigating, I noticed that I could still copy over the 4+ GB file to the flash drive, so it did not format the drive back to the previous disk format. I assume that format is FAT32. Unfortunately when I try to format the flash drive I am only fiven two options: NTFS and exFAT. I am going to try and locate some way to format to FAT32 and see if that fixes the issue.