1995 Altima no power to relay plug

No fuel pump and no ignition. That sounds like the immobiliser does not recognise the ECU or engine management system.
Good luck with that then!

Fusible links are either by the battery or down by the starter. But if everything else is working, this is not the problem You have a bad connection(pull the fuse and reinsert it or a broken wire). Most wires break close the the plugs.

starter,coils ,tune up,fuel filter,

All cars, EFI. (some have 3 fuse to operate ECU/spark/ fuel) check em yet?
check power to pump 12v cranking?
no, ? 12v, or 6v? (6v or near is corroded wires /conns)
check power (12v) from fuel pump relay cranking, got 12v there.
if yes , the the path is broken to the rear ) (inertial switch?, not in 95)
if not,12v now, the FP relay is bad or ECU is not turning it on.
if 12v is across the FP relay coil the ECU is working.
if 12v is across this relay, and output is dead, that is a bad relay
or the FI use feeding it is blown.
btw #1 all cars cut fuel (INJ) when spark is detected bad. (ecu)
btw#2 some (software) cut the fuel pump for same reasons.
btw#3, most cars, only activate the FP relay for 3 seconds key on, each time. and some cars only cranking, and running.
all these facts, need to be known to make progress, in EFI.
and more.

You may have a defective ignition starter switch, it is common in this year. When the switches go bad you loose power to the fuel pump circuit that power the relay.

the computer is what sends the signal to the fuel pump relay. Check the harness plug at the fuel pump again they tend to get loose. there is an updated replacement plug for this. also make sure the terminals on the fuel pump relay are clean and not corroded.

factory imobilliser has cut in by the sound of it ,you will have no spark as well at the plugs if iam right

Personally I wouldnt bother tracing the wire as it is probably not worth your time, and just run a constant 12v from the battery to the relay on like 10ga wire. There is probably a short somewhere in the system which can be a real headache to find.

Also it may sound dumb, but check your fuses, and the fusible links under the hood. Chances are that they are all fine though, especially if you have dash lights.

There are four relays under the hood on the drivers side fender. I think the order is main, ignition, ????, Fan. The second one from the driver is the relay for the fuel pump(ignition). Don't quote me, but I think you should measure 12v from both sides to ground when the pump should be on.