firmware upgrade Firebox T55 NFR
We have a Firebox T55 bought via WatchguardONE NFR, version 12.5.6 (Build 633773).
I cannot upgrade firmware directly from WebUI because of the message "You need a LiveSecurity key to upgrade your Firebox. Click here for help".
I know that the support was not extended... So, it'is ok that I cannot upgrade to the last firmware 12.9 (Build 672226).
But I want to know if I can upgrade to a previous version manually uploading the "T55.sysa-dl" from WebUI.
I found this thread on the community, but is referring to Firebox T70:
on that thread someone said that the user can install "Fireware 12.7.2 Update 2 will install on out-of-support devices".
And this is the page dedicated to the T55:
I see that there are many older firmware but I don't understand if I can install them or which one, without having the LiveSecurity key:
Fireware v12.8 Update 1
Fireware v12.7.2 Update 2
Fireware v12.5.9 Update 2
I do not know if the install is blocked with a message if i cannot install something; I do not want to brick my device and ask here....
I found that T55 is EOL on 2025.
But I do not think that is important for me (I mean, for upgrade now the device).
Could someone help me?