1) Open the m2 file with 010 Editor (no need to use M2Template)
2) Just look at the first line of 010 Editor
If you have something like MD21....MD20.... (16 bytes), it can't work on Wod, and you have to replace the 16 bytes by this in the hexadecimal part :
4D 44 32 30 10 01 00 00
3) Save and quit
Should work after that