So glad it’s working now, and good luck on the robotics project!
Just wanted to add a little more detail for others playing from home. As codewraith mentioned there are just two lines we’re interested in here.
So on your Picroft check the contents of your device level mycroft.conf file with:
cat /etc/mycroft/mycroft.conf
Make sure that the following two lines are set correctly:
"play_wav_cmdline": "aplay %1"
"play_mp3_cmdline": "mpg123 %1"
If they need to be edited you can do this by overriding them in your home directory:
sudo nano ~/.mycroft/mycroft.conf
then add the lines from above.