Unable to load JSON from URL

Hello, I was trying to use the scripts developed here to show my TRAINERROAD data on my iPhone. But the script only throws up errors.

I suspect that the url provided data is not able to be read/formatted by the script.

url : URL the script reads from

In SAFARI, the data is shown in kind of JSON format.
When I copy the string into a JSON validator it seems to be recognized as well.

I compared the script with others and it seems quite OK. I have the feeling the reading from url and then formatting of the string as JSON is not working. I also tried it in SHORTCUTS and there as well, the “Get contents of url” does seem to struggle. But being a newbie with this scripting - I am at a loss to be honest.

Anyone to help me resolve or understand this better? Many thanks !