Handoff for Safari, Mail, Notes etc. only works for a few hours max. When I try to use it after my iMac has been on for more than a few hours it refuses to work. The strange thing is, the handoff-icon DOES appear in my Dock, but when I click it, nothing happens, and in when I try it with mail it says 'Handoff cannot be completed'. From my mac to my iPhone the same thing happens. A restart usually fixes it. Turning bluetooth/wifi on and off doesn't fix it, and logging in and out of iCloud also doesn't work. My iMac is an 21.5 inch version from 2013, (Intel Iris Pro, 8GB RAM, Intel Core I5). Any suggestions on how to fix this? Or is the whole feature (2 years after it's introduction!) just buggy? It's really annoying, because Handoff is handy only when it works everytime, not intermittently. I don't see a reason to use it if I need to restart everything to make it work. Thanks in advance!