Had the exact same problem! Unable to Handoff from clipboard & native apps not seen by other device.
MacBook Pro M1, iPhone 12 Pro Max iOS 14.3
So, I tried advice Zuuti provided. Toggled Handoff on both devices, individually, with no joy.
I then turned off Handoff on iPhone, rebooted, turned back on..., JOY!
Clipboard Handoff back to working flawlessly, and both devices offer their currently used app/browser page to the other device.
Don't have time to add other devices to this Handoff 'fix' test, but will do so soon.
Bross2904
Users receive reputation points by contributing quality content to the forums.
Posts include post and replies published on the forums.
Post authors can mark replies as Accepted to indicate successful solutions.
Apple Developer Forums admins can mark replies as Apple Recommended to indicate an approved solution