Cannot Load M4a Files

[Lucile]

For over a decade I have used Express Scribe to transcribe dictation.  Now my computer, as of today, does not accept m4a files.  I finally converted them to m3a and it sees that format.

Am I doing something wrong?  Why will Express Scribe no longer load m4a files?  Please give me the proper steps - something has changed in a software that I have purchased for at least a decade.  I purchase updates when I have to do so, which is relatively often.  I am NOT using a free version of your software.

Thank you.