Always best to try to avoid the technological route and ask what was the last thing the human did, or did not do.
That thought has helped me for over 50 years !
A quick check is the socket where the life cable plugs in.
It can get damaged by debris or rough use during its life (no pun intended)
This is an example of the socket for the life ECU (whether it is situated on dashboard or on the sidewall of the cockpit). See how one pin has ‘retired’, it has been pushed back in plug so it cannot connect. The one in the picture is wired directly to the coms port so the PC can’t see the ECU at present.
Careful visual check on plug and socket will tell you in a minute if that is the issue and could save you from digging through software, etc. for weeks.
If it is like the example, it needs carful disassembly to make sure socket clicks back into place.
It’s a first quick check that has high percentage of success.
Check the lead too, to make sure the pin is not damaged, or debris is not pushing the socket out of the plug.
Hope this helps.