Cannot be located for screen sharing - Why?

He should uninstall all anti-virus software. All it does is bog down the system and apps.

OK; I'll get him to remove Norton. Hopefully that will get Screen Sharing working for his Mac.

For those download and run the free version of Malwarebytes. It was developed by a long time contributor to these forums and a highly respected member of the computer security community. 

Yes. Malwarebytes is a wonderful application - I can thoroughly recommend it!

But it's yours and his choice.

I understand the issues over malware applications for Mac, but I've only ever had good results with Avast. After running Avast on a slow Mac and removing malware it found, (especially AdWare) the speed of the Mac often improves. I appreciate that Macs can't get viruses, but they can get other forms of malware.

MacKeeper is a good example. Apple's OS doesn't block it, but it is a PUP which slows the Mac down a lot.

Another example in browser hijacks; where the Safari homepage is changed, and it can't be changed back.

That said, though, I will either try to avoid using Malware applications in future or at least disabled them if the Mac is having problems.

Thanks very much for your input; it's really appreciated.

The fact that you can connect to other Macs leads me to believe that it's the one Mac that has the problem and not yours.

Absolutely. I have no trouble connecting to most other Macs.

Even so, remove Avast.

This is a harder decision for me. Apart from this particular issue with only one other Mac, most things run well with Avast running, and it has found malware that the standard Apple system doesn't. Furthermore, I like the idea that it catches Windows malware too as this means I never unwittingly pass any application with malware to Windows users.

Is the Mac that you can't connect to different from those that you can, i.e. system, software installed (including anti-virus), etc. that would set it apart?

Not really, no. I successfully connect to several different Mac types and operating systems. That said, I know this particular Mac had Norton Utiititles Virus Protection on it, but he told me it wasn't working so probably isn't interfering with anything. But not being able to view his screen makes it hard for me to check! I did suggest he disable Norton - at least as a test - but as it isn't working anyway, he couldn't see how to do that.

Perhaps I should try to talk him through uninstalling Norton completely.

[Personal Information Edited by Moderator]

LOL. I don't understand why the Moderator had to step in because as far as I am aware, I blanked out the personal information!

But if I did wrong, I apologise!

If it worked previously with the same setup you have now try booting into Safe Mode

Actually, to clarify, this successfully connected to lots of other Macs; it's only this specific Mac which it won't connect to.

Copy the report and use the Add Text button to include the report in your reply.

Done.

Then we can examine the report and see if we can determine the root of the problem.

Thanks! Here's the report:

I notice part of the report said:

Problem: Other problem. Description: Mac wont connect to a remote Mac when using Apples built in Screen Share facility.

Same subnet? Does that mean same local network?

Sorry; I should have said: his Mac is many miles away from mine so we’re on different networks.

It's kinda crazy because I'm connected to remote Macs using this method many times. I just can't see why it isn't working in this case.