I have now tested mounting again with different formats. In fact, the problem of the hard disk not being recognised only occurred with FAT32. If you have the option to format the hard disk with exfat or ntfs, then it should work. Nevertheless, we will try to make FAT32 compatible as soon as possible.
Do you use a Windows PC? If so, you can format the hard disk via the disk management. Note, however, that formatting deletes all data on the hard disk.