Make sure your Gen light is good. If that bulb fails the whole circuit won’t work. Yes, it’s usually that simple.
To test the new generator, remove the fan belt and give it power from the battery using alligator clips: D+ to + and then – to case and DF (field). A good generator will spin like an electric motor (because it is). If that works, disconnect the battery, put the fan belt back on, tighten it right per the Bentley manual, wire the generator back up correctly and start the engine. You should get volts/amps out of it.
Vid explanation: https://www.youtube.com/watch?app=desktop&v=72XkA6LqCgg