After replacing the voltage regulator and alternator, the vehicle will still not start and stay running?

Hello, do you own a basic multimeter? There is a circuit that goes from the alternator through the engine compartment fuse panel and then to the battery. And those fuse panels being exposed to the elements can become corroded underneath, causing high resistance. So, with a few voltage checks we can see if there is any voltage drop occurring
I'll post some wiring diagrams to show the different wiring colors. It's a pretty simple circuit.

https://www.2carpros.com/articles/how-to-use-a-voltmeter

It sounds like the charging system is not working. I would charge the battery up and then start the engine, then while the engine is running let's check the alternator output.

Here is a guide to help:

https://www.2carpros.com/articles/how-to-check-a-car-alternator

The alternator might be defective. Here are the wiring diagrams for the alternator so you can see how the system works. There are 2 fuses that run the system, a 175-amp mega fuse (under the hood) and a 10-amp fuse in the interior fuse panel.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Let's test those as well. Check out the images (below). Let us know how it goes.

This is the engine compartment fuse panel.