Work is underway on a fix for JSON output for the WMS Collection Management API. Users reported problems after last weekend's update and our investigations revealed that while the atom+xml output is working as expected, the JSON output is currently unavailable. We have identified the cause of the problem and are working on the resolution. We are making every effort to improve our processes and prevent similar problems from occurring in the future.
We are currently planning to install the fix late next week. We will post an update here on Developer Network when the fix has been installed.