The TM-6 PRO will display "Unsupported Format!" if you attempt to import an audio file that isn't compatible.
The TM-6 PRO can import .wav files that are 16 or 24 bit, with a sample rate of 44.1kHz.
Make sure you transfer them to the Import folder on the SD Card (Do not place them into any other folders that may be on the card).
Audio that was purchased from an online music store such as Amazon or iTunes, or ripped from a CD, are usually MP3 (compressed) or m4a audio files and will not import into the TM-6PRO. You can use iTunes, Windows Media Player, Audacity or other free programs available on the internet to convert these files to .WAV. Refer to your program's documentation on how to perform this conversion.
If you're sure you have a .wav file that matches the criteria above and it still won't import into the TM-6PRO, then the file may have embedded metadata, or "tags," that are causing the error. This can happen with files that have been created in DAWs ("Digital Audio Workstations"), other audio programs, or sample libraries. You can strip this extra information from the file by converting it to Apple Lossless or FLAC format. After converting to Apple Lossless or FLAC, convert that file back to .wav 16 or 24 bit / 44.1kHz.