If the header is damaged, and the file is IMA ADPCM (as reported by VLC), the Audacity will probably not be able to read it.
If it plays in VLC, then you could use VLC to convert it to another format (such as 16-bit PCM WAV).
If VLC can’t play it, then the file may not be recoverable, but if it is extremely important, there are (expensive) professional data recovery services available (search on-line, and check their fees and reputation).