iCloud folder sharing seems to be down

Users A and B have a shared family iCloud account, each with their own login.

Person A uses iCloud for Windows on Windows 10, and years ago created a folder and shared it with B. This has been working with no issues.

Yesterday, the shared folder disappeared from all of B's devices, leading to temporary panic until A verified that the shared folder is intact, but A seems to have become disconnected from it for unknown reasons.

What A currently sees:

• In iCloud on an iPhone and iPad, the shared folder no longer shows up as shared
• In iCloud web, attempting to re-share the folder times out with "People couldn't be added. There may be a problem with the server. Please try again later"

Is Apple experiencing a problem with their servers?