My iframe stubbornly stays at one size

[BlazingCobaltX]

Hi all, see this page: https://blazingcobaltx.neocities.org/musicroom/jukebox

By pressing any of the images an iframe appears into the container next to it. I would like this box to be a bit longer, but every attempt at adjusting the height of the iframe or the container itself are met with no movement. Am I missing something in the code or is this related to a property of the iframe itself? Ideally I would like both boxes to be of equal size.