Nostalrius Begins - Quality wow vanilla realm (1.12)

Hi, today I downloaded the provided client and installed it in the recommended directory. When I open the game there's no AddOns button anywhere to be found, I'd like to use some addons and this issue is making it impossible. Can I get some help please?

AddOns button will not appear until you actually have some custom addon(s) installed in the proper place.

<wow install directory>\Interface\AddOns\

I did install some addons, but it didn't fix it

Do you have multiple WoW installations? Are you sure you're looking at the correct one?
Right-click the shortcut you use to launch WoW and "Open File Location" (depending on your OS it might be "Properties" > "Open File Location")
Then you are sure you're at the right installation folder.
If you verified you're at the right installation folder and that's not the problem look below.

Are you on Windows7 or later?
Did you install WoW in C:\Program Files\ or C\Program Files(x86)\

If answer to both questions is yes then you've fallen victim to Windows VirtualStore.
In Windows7 and later the Program Files directory is considered protected so applications trying to write to it end up creating the files in the VirtualStore which is at an entirely separate location.

The easiest way to fix it is to move your whole World of Warcraft directory from inside Program Files to another location like C:\Games or D:\Games or whatever, just somewhere that's not a protected location.
Then update your shortcut to point to the new location of WoW.exe.
First time you start WoW from the new location it will update the registry etc on its own, you don't need to re-install.

He said he is using the provided client. That client is modified by nost to have its Interface and WTF folders not within its own folder but they are in your users folder. (Can't pinpoint the exact path right now since i don't use that client) Something like C:\Users\<username>\Documents or AppData.

Real installations I only have this one, the other I have is not installed, it's just a folder with an .exe inside and some files, which is the WotLK.
I have Windows 10 and installed the game directly in C:\

My interface and WTF folders are inside the game's folder, they're not in users' folder.

What happens if you try to right-click your WoW shortcut and "Run as Administrator"?

The same thing that happens when I run the game normally

I still suggest you move the whole World of Warcraft folder a level deeper, not directly under C:
Make a C:\Games\ folder and move it in there, then run the WoW.exe and see what happens.

I just did, but it didn't solve it either :/