@Steve-Mcl the flow is using readBigInt64BE so it must be node 12 or later.
As I've already said, the problem here is what the flow is trying to do with the result of readBigInt64BE.
@Job-Hoogeboom in your screenshot we can see the errors, but we cannot see what node has reported them. Can you tell us which nodes are logging these errors? Click on the node ids I've highlighted.
in your screenshot we can see the errors, but we cannot see what node has reported them. Can you tell us which nodes are logging these errors? Click on the node ids I've highlighted.
The code in Steve screenshot was just to simulate what you are doing to show there's a problem with the Debug node. It wasn't code for you to copy.
Now we know the Debug node can't handle BigInt, we can ignore the error it is produce - it won't affect your flow from trying the HTTP request to Datacake.
So where have you got to with that part? Is it working?