Undertale genocide ending didn't work?

[Emma]

Before I tried doing a genocide route on undertale I did the pacifest route two times. Then I decided I wanted to do a genocide route, so I tried. I killed everything but it was nothing like the genocide route is supposed to be, according to other articles I've read. In my genocide run I killed everything, but I didnt fight Undyne the Undying, Mettaton NEO, or sans. I didnt even encounter them. I fought Toriel,Papyrus, Undyne, Mettaton Ex, King Asgore, and Flowey, just like you do in the Pacifest route except I killed everyone. I've heard that you fight sans in the hallway leading to Asgore when he judges you, but he didn't fight me, although he did reconize that I killed Papyrus. Then after I killed Asgore and Flowey, I got a phone call from sans and he was talking about how things are rough in the underground because I killed everyone and he is just really ♥♥♥♥♥♥. Sounds like a nutural ending? I killed everything and didnt' get a genocide ending. I'm guessing it's because I had played a pacifest run before that, but how do I get the real genocide ending? Do i have to reinstall the game for it to be able to do the real genocide route?
EDIT- when I start the game again and do a reset, instead of flowey talking to you at first, Toriel just comes out and the game just skips over the part where flowey talks to you.

[pupu]

Sounds like you mistakenly did a neutral route. In order to do the genocide route, you must grind in each of the main four areas (Ruins, Snowdin, Waterfall, & Hotlands/Core). Grinding encounters means you kill everything until you receive the "But nobody came..." message.

[Emma]

Originally posted by ℭystenn:

Sounds like you mistakenly did a neutral route. In order to do the genocide route, you must grind in each of the main four areas (Ruins, Snowdin, Waterfall, & Hotlands/Core). Grinding encounters means you kill everything until you receive the "But nobody came..." message.

I'm fairly certain that I killed everything, and what's the "but nobody came" thing about? How and when do you get that message

[ditt_25]

You didn't kill EVERYTHING then.
The game will make it VERY OBVIOUS when the kill everything for an area is complete.
Taking 5-15 mintue between fights IS NOT "very obvious."
You need to intentioanlly grind encounters.

Certain rooms cannot have random encounters (even if they have spiked tiles)
Changing rooms resets the timer until the next fight.
One effective way is to just had to a wall and hold both up and down at the same time if you still desire to do this foolish thing.

Be good,
won't you?