https://imgur.com/a/e76EmH9

I'm not sure what your problem is, I tested several buttons and they didn't have issues. If you send a photo or video of your game and code, I might be able to see what went wrong.
Other than that, all I can tell you is to make sure all of your buttons are identical, just to narrow down the inconsistencies.

I have the same problem. First godot 4 doesn't exist in the play store but godot 3 do . And when i try to create and edit the project it chow me the godot logo but it crach and say godot has stopped. I been really happy when i heard that godot is in mobile but now not

@lemu_kymoh I'll put the exact code I'm using. (I made things less specific for the sake of the original post.)

Well as it turns out you're right! It worked. I'm not really sure what went wrong with the other tutorials...

The video was really helpful.
I watched it in slow motion and I realized that for all of your shots (not just horizontal), your grenade would go upwards just a little bit, then quickly corrects itself to go the right way. So it seems like something in the grenade code is making it go up when it gets made.

Sure enough, the direction starts at Vector2.UP, and the _process function makes it move in that direction.
But at the same time, in the "Level" scene you properly set the grenade's "linear_velocity" to its direction right after making it. So my thinking is that it takes a little bit of time to set the linear_velocity so the grenade defaults to going up for a split second.

I believe the solution would be to make the starting direction (in Grenade scene) to Vector2.ZERO, that way it doesn't try to move when it gets made.

Some stuffs are cached in Godot Engine, so it might not refresh yet. But you can force it to reindex everything:

I'm using 4.1.1 stable,

the first 2 lines seem to have worked (weirdly) and yes I get the error:
Line 11:Identifier "_connected_to_server" not declared in the current scope.

What could I use to get around this problem?

This is the tutorial I'm following:
Godot 3 Networked Multiplayer Shooter Tutorial

The variable joystick isn't instantly ready, so at some point it's null variable, until get_node has finished the job. Try doing it like: