The issue is likely regarding the time when the Slicer preview build finishes and is available to download versus when each extension finishes and is available to download. This time difference is not an issue for people in the USA as the build time is not during regular work hours. For example it is 8am on the east coast and most extensions are built and available to download however there are some extensions just now finishing up but the entire process will be over soon. See the CDash column for start times of the preview build and each extension here.
See the linked post below about the topic which also includes a link to a Slicer GitHub issue that tracks it as well.