Won't run

You have to determine which function is dropping out whern this happens.
Here is the testing sequence.

All "crank, no start" conditions are approached in the same way. Every engine requires certain functions to be able to run. Some of these functions rely on specific components to work and some components are part of more than one function so it is important to see the whole picture to be able to conclude anything about what may have failed. Also, these functions can ONLY be tested during the failure. Any other time and they will simply test good because the problem isn't present at the moment.
If you approach this in any other way, you are merely guessing and that only serves to replace unnecessary parts and wastes money.

Every engine requires spark, fuel and compression to run. That's what we have to look for.

These are the basics that need to be tested and will give us the info required to isolate a cause.

1) Test for spark at the plug end of the wire using a spark tester. If none found, check for power supply on the + terminal of the coil with the key on.

2) Test for injector pulse using a small bulb called a noid light. If none found, check for power supply at one side of the injector with the key on.

3) Use a fuel pressure gauge to test for correct fuel pressure, also noticing if the pressure holds when key is shut off.

Once you have determined which of these functions has dropped out,
you will know which system is having the problem.

OK, finish the rest of the testing and post what the results were including the pressure reading.

Of course it flashes when it's running, otherwise it wouldn't be running. We need testing at the moment it's refusing to start.

Yes, and you didn't finish the rest of the testing at that time.

Did the injectors still have power supply when that happened?
Did it still have spark when that happened?
Did it still have fuel pressure when that happened?

I'm asking about power, not pulse. Were both checked?

I'm finding that result pretty hard to believe but the power for that is supplied by the "ECM" fuse but fuses aren't known for going in and out for no reason. If you're giving me faulty test results, you're the one that will be chasing up the wrong tree.