Hi Maria! Can you please clarify if you saw an error message specifically saying "missing media files?"
If you did see the "missing media files" error, please download your curriculum file from your account page (
Account > Purchases > Little Musician Curriculum & License Key).
If you downloaded your curriculum file already but some slides appear blank/empty (e.g., in some Instruments slides the picture slide is followed by a blank screen instead of showing a video), please follow the instructions here:
http://support.brillkids.com/hc/en-us/articles/204598754-The-Videos-in-the-Little-Musician-Lessons-Aren-t-Playing-Back