@Zainab ,
I just learned something new today. If I don’t have a stylers.xml, and I hadn’t previously selected an existing theme, and the install directory (the one containing notepad++.exe) doesn’t include stylers.model.xml, then Notepad++ prompts with a dialog that tells me loading stylers.xml failed, like:
3059d3f3-9683-4954-886c-a297fb5e2c86-image.png
…if I OK from that point, Notepad++ loads, but if I try to launch Style Configurator, nothing happens. This seems similar to your circumstance.
(yes, the way i accidentally reproduced your problem was by launching a copy I had built without having the right XML support files while running in doLocalConf mode)
It gives me that same error if I had Dark Mode chosen, so it was using the DarkModeDefault theme selected, but still had no stylers.xml or stylers.model.xml existing, but then deleted DarkModeDefault.xml and restarted Notepad++.
Given that you seem to have the Dark Mode in your screenshots, but the new 1 looks more like normal light mode, which matches what I saw in my Dark Mode experiment, I am now hypothesizing:
You had selected Dark Mode, and one of the dark themes (possibly DarkModeDefault, or any of the other dark themes)
Your copy of stylers.xml was deleted (or you changed to an alternate config setup, like cloud or --settingsDir or doLocalConf), and your copy of stylers.model.xml is not in the same directory as notepad++.exe
You ran Notepad++, and saw that dialog, but closed it and neglected to tell us
If you can re-populate stylers.model.xml (grab the official zip download, and copy the stylers.model.xml from that and put it in the same directory as the notepad++.exe that you are running), then re-start Notepad++, then it should not give that error, it should create stylers.xml from stylers.model.xml, and the Style Configurator should be able to launch again. (And if you want, you can also copy the themes from the zip to your <install dir>\themes folder to give you access to the other themes as well)
Sharing your debug info (?-menu, Debug Info, Copy debug info into clipboard and paste into your reply) could confirm for us if you have a non-standard installation or portable Notepad++, which will help us be more specific about where to look for files and where to put them
update: also, I noticed that you have logged in since our replies, but didn’t respond to any of our requests for more information. We won’t be able to help you any farther if you choose not to respond so that we can try to help you more. The ball is in your court at this point.