Cannot open files on another iMac

We have two iMacs at home that we regularly connect between using Go>Connect to Server, etc.

I can connect from my wife's iMac 1 to my iMac 2 using my login/password and see my folders, but I can't open them or see their contents as I could previously (probably a few months ago).

iMac 1 is a Retina 5K, 27", 2017 running Mojave 10.14.6

iMac 2 is a 27", late 2012 running Catalina 10.15.5

We haven't updated Mac 1 to Catalina as I am copying HFS DVDs onto the drive as Catalina doesn't support HFS files...whinge, whinge like others!

Update: now when I try to connect to Mac 1 from Mac 2 its image appears with Not Connected message bu when I click on Connect as...nothing happens.

Both Macs are set up for file sharing...in fact, no settings have changed since the last time I transferred files.

What have I done wrong?