Sites like Restore.Media or Online Converter specialize in fixing M4A files that were cut off (e.g., phone died during recording).
If the file doesn't have a proper dot before "m4a," try renaming it to RecordTMP (32).m4a to see if your computer recognizes it. RecordTMP (32) m4a
Apps like GarageBand or Audacity may create .tmp or RecordTMP files while you are recording to ensure data isn't lost if the program closes unexpectedly. How to Access or Fix the File Sites like Restore