Worlds Cannot Upload to Realms

Since the last update, I have been unable to upload local worlds to my Realms account on any platform, even after reinstallation on all platforms. In most cases it sticks at “Initializing Upload” for an unusually long time before giving an error. From time to time it will stick on “Initializing Upload” and never get any further. No matter how many times tried, the worlds never upload to the Realms account.