Custom textbox doesn't appear in-game

[DBMalachite]

I'm trying to give each character their own custom textbox but when I use the following code:

define k = Character("Kia", color = "#e27a24", window_background = "gui/k_textbox.png")

No textbox appears, only the character's name and dialogue.
The custom textbox is the exact same size as the regular textbox so I don't think it's off-screen.
I'm new to using Renpy so I apologize if this is something really simple to fix!

[Per K Grok]

I'm trying to give each character their own custom textbox but when I use the following code:

define k = Character("Kia", color = "#e27a24", window_background = "gui/k_textbox.png")

No textbox appears, only the character's name and dialogue.
The custom textbox is the exact same size as the regular textbox so I don't think it's off-screen.
I'm new to using Renpy so I apologize if this is something really simple to fix!

The script looks correct. I suspect there is something different with the k_textbox.png image.
If you open up the ordinary textbox image and the k_textbox image in a graphic editor as layers, do they really match up with each other?

[DBMalachite]

Both textboxes were the exact same size as each other but I think I figured out what I did wrong. Both of the images were as large as the game's resolution and when I put them into an image with less empty space it worked.