I don’t expect to have to do this again but include it here just in case I do or it helps someone else avoid what I went through. Essentially, you cannot use the latest version (2.05.05) of the Netgear Smartwizard software to update the firmware of this switch. I had to use 2.05.03. Note that I suspect that this applies only to v1 of the GS724T.
I spent hours resetting the switch to factory, restarting, trying various operating systems, trawling websites etc without any luck. Every time that I tried to upgrade firmware, it failed with a message similar to this:
“trigger failed. device does not exist”
Eventually, I found this page:
which suggested that an older version of Smartwizard software was required. After trawling the web again for awhile without success, I searched through cd’s in this office and stumbled across an old Netgear CD which turned out to have Smartwizard 2.05.03 on it. Firmware update worked perfectly! Thank God for someone’s hoarding streak!
Drop me a message if you need a copy of 2.05.03.