Q: problem connecting macs over the network

If computers are on the same network suggested article : How to connect with File Sharing on your Mac - Apple Support

cadplan45, go back to basics…

1. Reboot everything.
2. All of these devices are on the same network - are they all using wifi, ethernet or a mixture to get on the network? Try to use the same type of connection & retest.
3. This network allows internet access? If so can all of the devices view the web OK? - e.g. basic networking is OK.
4. Can these devices 'see each other' in Finder use 'Go menu > Network' to browse the local network. Can each Mac 'see' the others?
5. All of the Macs still have sharing enabled - double check that in 'System Preferences > sharing', also make a note of the 'Computer name' listed there.
6. Try connecting to each Mac using this in Finder 'Go > Connect to server' enter the 'Computer name' from step 5 for each Mac you want to view.

There are questions that you are meant to answer in that list…

All of these devices are on the same network - are they using the same connection type?

In Finder use 'Go menu > Network' to browse the local network. Can each Mac 'see' the others?

Also what is the result of connect to server? Does that only fail for the iMac to the Mac Mini, what is the error dialog?

Sorry I can't help if you don't give appropriate feedback.

Hmm, the shaking dialog does sound like the username or password are rejected.

Can you double check what your username is on the Mini. You can use either the 'Full name' as shown in System Preferences > Users & groups or the 'short name' which is generally the same as the home folder for that user (has no spaces in the name).

If you have several users on the Mini try all the user accounts.

On the Mini do you also have any of the options set in 'System Preferences > Sharing', such as AFP or SMB?

SMB sharing allows you to select specific users, so look in the options sheet to set that up. Compare to a working Mac if you need a reference.

When you enable SMB for a user it will prompt for that users password, so toggle the user & enter their account password.

Am I missing something - isn't the Mac Mini the issue here? Did you disable & re-enable sharing on that Mini or just the iMac?

I can't see how the network card would simply fail to allow one network service to work for one Mac. Hardware issues would normally cause the Mac to fail to network at all or have very specific issues (like not boot over a network). A configuration or software error seems more likely to me. I'm assuming the iMac is otherwise networking OK as you haven't mentioned other issues (it works OK on the web etc).

If you want to test the hardware try ruling out your current software by a process of elimination…

Install OS X to another disk (a USB bootable disk can work provided it is not a slow thumb drive). Reboot to that OS, setup file sharing & if that works you know the issue lies in OS X or it's settings on the original disk.

Obviously this can take a few hours to setup so ask if you want help to do it. You will need to have the OS X installer downloaded from the store & also a spare disk to erase & install OS X onto.

The problem you have is that the issue could be in the Mini or the iMac - so you would need to setup a 'clean test install' on both Macs to try at the same time.

You may want to consider another step first…

Make a new user account in System Preferences > User & groups on the Mini, try connecting via that account from the iMac.

Repeat on the iMac, add a new user, login as that user & try connecting to the Mini - just log out all other users first.

I suspect there may be log messages that could help with diagnosis but I'm not sure which end to look & which specific log file(s) to look through, sorry.