File and screen sharing no longer work in El Capitan

I can no longer use file sharing or screen sharing

What exactly happens when you try?

Working just fine for me between Macs with 10.11.5. So it is not broken in 10.11.5 but only in your configuration.

Please read this whole message before doing anything.

This procedure is a diagnostic test. It’s unlikely to solve your problem. Don’t be disappointed when you find that nothing has changed after you complete it.

The purpose of the test is to determine whether the problem is caused by third-party software that loads automatically at startup or login, by a peripheral device, by a font conflict, or by corruption of the file system or of certain system caches.

Disconnect all wired peripherals except those needed for the test, and remove all aftermarket expansion cards, if applicable. Start up both Macs in safe mode and log in.

Note: If FileVault is enabled in OS X 10.9 or earlier, or if a firmware password is set, or if the startup volume is a software RAID, you can’t do this. Ask for further instructions.

Safe mode is much slower to start up and run than normal, with limited graphics performance, and some things won’t work at all, including sound output and Wi-Fi on certain models. The next normal startup may also be somewhat slow.

The login screen appears even if you usually login automatically. You must know your login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.

Test while in safe mode. Same problem?

After testing, restart as usual (not in safe mode) and verify that you still have the problem. Post the results of the test.

Having this same exact problem. Screen sharing has always worked flawlessly; after an update to 10.11.5 to all Macs in my household, now I'm unable to use screen sharing from/to any of them. I verified firewall rules, sharing properties, etc. Seems to be a buggy version/update that crippled the feature. Very frustrating. Guess we are SOL until 10.11.6 (hopefully!)

I have very similar issue as the OP since the 10.11.5 update. Sometimes my shared Mac that also has the last update doesn't show up in the Shared section of the Finder sidebar and sometimes it does. When the Mac does show up sometimes connecting works and sometimes it fails.

Another of my Macs that is on the previous version of El Capitan always shows up and works. It also seems to show the updated Macs in sharing and connections have been working whenever I've tried them but I don't use that feature often.

I don't have a fix but this is a workaround that has been working 100% of the time for me.

On the computer which you wish to share go into System Preferences > Network and make a note of the IP address. Then go to the finder on which you wish to use the shared computer, choose Go > Connect to Server… and type in the IP address. You can then choose what from the shared computer you wish to use. The IP address is saved as a favorite so you don't have to type it in every time you connect.

A few months later and I'm seeing this on 10.11.6. We are having this problem but it is intermittent. Sometimes I can see the shared computers and router in Finder's Sidebar, and have no problem to paste files in the dropbox. Sometimes not even "Shared" shows up in Finder's Sidebar. This did not happen directly after I upgraded to 10.11.6 but after I migrated to a newer iMac. All my settings and preferences migrated just fine, but sometimes this one problem shows up. I have repeatedly checked Finder's Preferences to verify they should show all Shared in the Finder Sidebar, but often nothing is there. It shows "Favorites" and "Devices" but I frequently need to use email or a flash drive to share files with others in the same room.

I wish I knew how to help you but I'm hoping a solution will come through here. Good luck!