Hi, I have been able to work it out, much to my embarrassment, but hopefully 
helpfully to someone in the same situation.

I restarted all 3 iMacs and I was able to instantly find each one on the other.

Adam sent me an attachment from Brother support as to the proper way to 
configure the printer for the 5G network and that issue is resolved to.

Thanks

Matt.
 
>   1. Connecting iMac to iMac with 5G (Matt Falvey)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Sat, 8 Oct 2022 18:14:18 +0800
> From: Matt Falvey <mmfal...@bigpond.net.au>
> To: wa...@lists.wamug.org.au
> Subject: [WAMUG] Connecting iMac to iMac with 5G
> Message-ID: <1a2c53a3-25f0-4aca-b387-d5125b3be...@bigpond.net.au>
> Content-Type: text/plain; charset=utf-8
> 
> Hi, I have just joined Telstra 5G to improve my NBN download speed from an 
> average of 27 Mbps.
> 
> I normally have 3 iMacs linked via wifi but since I have started using the 5G 
> I have been unable to link them up. I normal do so by Finder>Go>Connect to 
> Server and then using either the smb of afp favorite servers.
> 
> Also I have been unable to get my Brother HL-L2375DW to show up or even to 
> link that through any of the 3 iMacs. I have tried using the Brother 
> Instalation disc and it can?t find the printer over the wifi.
> 
> Anyone have any idea as to how I can get things linked up?
> 
> Thanks
> 
> Matt.
> 
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