Empty linear chart- what to fix?

Hi everyone,

If you have time, can you assist me to understand the reason what is not working in the script I used from the webpage Line plot with several groups in d3.js

I would like to create a grouped linear chart see: https://dads-adv-d3js.grotebroer.repl.co/ , but the line does not appear and have no clue what to fix.

Thanks in advance.

Best regards,