Exporting error

[OMVMMG]

I'm getting this error when exporting:

ERROR:main:export_audio
Traceback (most recent call last):
File "/home/test/piper-recording-studio/export_dataset/main.py", line 107, in call
audio_16khz_bytes = subprocess.check_output(
File "/usr/lib/python3.10/subprocess.py", line 421, in check_output
return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
File "/usr/lib/python3.10/subprocess.py", line 526, in run
raise CalledProcessError(retcode, process.args,
subprocess.CalledProcessError: Command '['ffmpeg', '-i', 'output/en-GB/4000000001_4000000300_CustomerService/4000000006.webm', '-f', 's16le', '-acodec', 'pcm_s16le', '-ac', '1', '-ar', '16000', 'pipe:']' returned non-zero exit status 1.

Any ideas what is going on?
Thank you for your help.