Initializing error: Not supported MIME-type

URL of experiment: https://gitlab.pavlovia.org/DuderstadtV/leson_square_bugtest

Description of the problem:

Dear all,

I want to do a fairly complex online experiment with a lot of Python-code to debug. Because it is my first online-experiment I started only with a part of the whole experiment. Unfortunately I can not start to debug the code, because my studies don´t get initialized with the reminder that I my data sheet doesn´t has a supported MIME type. I compared it with other studies and it seems during the conversion from builder to gitlab the necessary Javascript sheets have not been created into the html folder. Does anyone know what could be the problem?

Best regards,
Vinzenz