Incomplete message history on multiple devices after iOS 26 update and iCloud storage upgrade

I show 58K messages in iCloud but I can only access my last 30 days of messages on 3 of my 4 devices. Until last week I could see complete message history on all 4. How can I again gain access to the full history on all 4 devices? I upgraded my iPhone 16 Pro to IOS26 and expanded my iCloud storage to 200GB last week.

[Re-Titled by Moderator]

Original Title: Messages and iCloud