Your responseContent is not well formed JSON text.
It needs [ ] at file begin and end and ',' between each object and the next, to make it a list of objects.
Use Do It on the output of your JSONTextDecode attempt for confirmation.
KIO4_DecoJson extension can be a bit complicated to handle, but if you do it right it uses less blocks, in image you get the data of the record whose id is 20110003.
If you prefer to use the JsonTextDecodeWithDictionaries block, I imagine that would be a good option as well.