Hi @SamKr I have the same issue recently, and I solved making a Reconfiguration of the Locales with the next command
sudo dpkg-reconfigure locales
I was following the next link
I really dont know how this resolve it 
but it works for me. I use the option “all” locales and it take a bit long to finish the reconfiguration but mycroft started listening to me 
About the configuration file, I found it in …/mycroft/configurations/mycroft.conf
PS: sorry if i struggle with the english 