Yes, I followed your sorrows in these fora at the time, as I've been on the look-out for a 2400.It could be the PMU playing up. Mine did this and the procedure for getting it up and running again is somewhat hit-and-miss.
From memory you need to unplug the machine from the mains, remove the main battery and then leave it for some time (the advice I remember is over-night but I seem to think that a couple of hours was enough). Then hold down the reset switch on the back for 30 seconds. Re-connect the power, hold down the reset switch again (for another seconds) and then try powering it up.
On my machine this worked for a while and then gave up the ghost (like you I removed the PRAM battery thinking that it'd help - I'm not certain whether it did or not)
If you do get anywhere with the fuse then I'd definitely be interested to know what you did
I still can't make it boot, but will persist a while longer before abandoning the attempt, given that the reputation of the machine is one of extreme temperamentality. I have wondered elsewhere whether I could try recharging the backup cells in my Duo (2.4v in the Duo vs. 3.6v in the 2400, however - but I don't think I have any machines using 3.6v pram cells, and would not want to try it in something that recharges at higher voltage, like a Wallstreet). Alternatively, I suppose I could jury-rig an ordinary 3.6v Lithium just to see if it would awaken the 2400 - if the main battery does not charge, 'tis said, the machine will not try to charge the backup battery, so no explosion for the purposes of the trial. Hmmm. Any opinion on that one? It would only be in there for a few minutes.
Failing this, I'll likely just disassemble it and bring the boards/ cards to a specialist for component-level (i.e., SMT fuse) testing/ repair. The result would certainly be more reliable than if I tried to do it myself! I can do many things, and some of them I even do rather well, but these things do not include component-level electronics repair.
All in good time.... Having just bought the thing, I'd best save my pennies or flog some spare gear in order to finance the next phase. Otherwise the hobby becomes a little too absurd.