Failed to update data source credentials from web

Hi,

I have seen this being asked planty of times, but can't find a solution to my issue. I have just taken over a dataset and put mysdelf as the dataset owner. Then, obviously had to re-enter the credentials.

I have a table with web content, but keep getting the error message below. Not sure why. It refreshes fine in desktop. This is a web api source. 

Apologies if this has been asked before, but help is appreciated.

Thanks!