the app support both exFAT and FAT32 so that should not be a problem. Also on a PC formatting should not have changed the partition scheme unless you told it to use GPT (called GUID on Mac).
If you have a mac you can use disk utility and partition and format the drive. Make sure the partition scheme is set to MBR (Master Boot Record) and use either MS Dos file type (FAT32) or exFAT.
