Serious bugs in ChatGPT for Windows and Web browser: Why aren't the new models working?

For the past few days, I’ve been encountering an issue where, whether I’m using a web browser or the ChatGPT app from the Microsoft Store on Windows (which is essentially a web browser wrapped in a more convenient interface that still has many flaws, such as not remembering the window size from the last session and having a somewhat flawed interface), no matter which model I choose—whether it’s GPT-4o, GPT-o1, or any other—the app consistently responds as if it’s using the old GPT-4 model. It refuses to Google, think, process images, files, or write code. It states that it can’t perform these tasks and that its knowledge is limited to the last update of the database from October 2023.
I am a user with an individual Plus subscription, and my limits (which are already quite small) haven’t been exhausted.
There is no such issue when using ChatGPT on the iOS app. This is a specific glitch on Windows and web platforms.