The drive itself is compatible with the 2 operating systems, the FILE SYSTEM is not. You can format any drive as you like it and it will behave as the FILE SYSTEM tells it to behave. If it was working on your Mac then the FILE SYSTEM was changed to HFS+ (No restrictions on OSX), which means that it no longer works on Windows because Windows doesn't support ANY external drive formatted as HFS+. Opposite is also true, if you format the drive back on Windows then the drive will become NTFS (No restrictions on Windows) and will work on Windows, but your Mac WON'T be able to use it.
If you want it to work on the 2 systems, then format the drive as FAT32, it will work on BOTH but won't accept any file larger than 4 GB, won't do automatic backups and will have a higher risk of data corruption. THAT APPLIES TO EVERY SINGLE INTERNAL AND EXTERNAL DRIVE EVER MADE BY EVERY MANUFACTURER.
That Windows and OSX hate each other is not a drive fault.