Universal Clipboard suddenly stopped working (literally as I was using it)

I have made extensive use of Universal Clipboard for a long time. It has always worked. Today, it stopped working - in both directions from/to MacBook Pro and iPhone 16 Pro Max - for no apparent reason and with NO changes to iCloud account or settings/OS on both devices whatsoever. It worked - then it didn't !!

Yes to:

• I am signed in to the same iCloud account on both devices (I only have 1 account)
• Both devices are connected to the same WiFi (I only have 1 WiFi)
• iCloud, Internet and Web work perfectly on both devices
• Both devices have Bluetooth enabled (and working)
• Both devices have Handoff enabled
• Devices are within a few centimetres of each other
• Both devices are up to date (macOS Sequoia 15.4, iOS 18.4)
• Both devices have been shut down and restarted, iPhone forced restarted (several times)
• Airplane mode has been cycled on/off on iPhone (several times)
• WiFi, Bluetooth and Handoff have been cycled on both devices (several times)
• Copy & Paste work on individual device (eg. copy on iPhone paste to iPhone/copy on Mac paste to Mac)
• Tested to/from several apps on both devices (eg Mail, Messages, WhatsApp, Outlook, Word, etc.)

Evidently, a copy on either device is not being sent to or stored on iCloud. Or a paste stored on iCloud is no longer being downloaded.

Besides being annoying - this is a major blow to productivity.

Appreciate if anyone can offer a resolution. Thanks.