It works fine without epansion board, see also https://www.dfrobot.com/forum/topic/312660

Do you mean between RasPi and Expansion Board?In this case, no.

Hi,

We have made some progress and have found that it is because the io extension hat huts off after a while. When the board is working we get distance readings. After a while the extension shuts off. Is this a defect or a setting issue? 

Thanks for the support in advance!

No difference, still no data. I don't see any difference in the code either.