With the new REST nodes when I check "Fail on http errors" the node fails when a response code other the 200 is returned. This is the correct behaviour; however, my suggestion for an enhancement would be to allow the user to then inspect the error code and any response messages so that the cause of the error can be determined. Currently you have to uncheck the "Fail on http errors", re-execute the node, and look at the results. This is kind of a pain. Thanks.
we just opened a feature request for you. There will be a warning message in the future.
Best regards, Iris