In RDR: Undead Nightmare, there is a cheat that spawns a coach (wagon) For some reason, I cannot use this cheat because when I try, a message telling me that I cannot use the cheat because of my current activity.
Is this a glitch? If so, how do I fix it?
What are "activities"? How can I get rid of them so I can access this cheat?

I have read the Undead Nightmare manual and have not found out what these activities are.

I'd assume it's because you have a mission, do you have any quest markers on the minimap?

There's the conservation quest deal in which you hunt sasquatch.
Also, I'm on the mission in which I have to collect violet snowdrop and some other things for the old salesman.
Will I have to find those ingredients before I can use the cheat?

There's certain cheats that don't work undead nightmare and only work in the base game. The coach cheat might be one of those.

Theres no coaches pre cheat, so none would appear

Now I have another problem. I can't seem to find a Rolling Block (sniper) rifle. I have beaten the game and saved every settlement but I still haven't found one. Early on in the game I used a gun cheat that gave me a bunch of good weapons, but no rolling block. I know that there is one in Undead Nightmare because I have played it on a friends profile and he had a rolling block.

Maybe the game is just punishing me for being such a noob and using cheats...

I think you get it from saving the Pacific Union Railroad camp settlement. If you didn't get it the first time, just wait till it comes under attack again.

:facepalm: I cant believe I didn't think of that.

I had accidentally killed one of the non-zombie guys and everyone started to shoot me, so I left them at the mercy of the undead.

It's the only settlement left, so that's where it must be.