Sometimes, I’ve found, especially in FM23, the game just won’t read certain jpg files, even though there is no obvious reason.
If you are updating images, with ones you’ve found on the internet, occasionally, when looking at the image properties, the image will be “locked”. Try unlocking. Sometimes works.
The alternative is find another image. I’ve said this before, but when trying to find a stadium background image that the game would read, for the Cuban national stadium, I had to burn through 5 different files before finding one the game was happy with. For no obvious reason.
If all else fails! I have also had to create a new folder, that sits at the top of my backgrounds folder (name it 0-whatever) that has its own config file. For REALLY tricky image recognition. The game reads configs in the graphics folder in positional order. So if there is a conflict somewhere your new folder will be read first, and hopefully show the image you want.