Sometimes Miracast hides under a different moniker. My Samsung Android tablet calls it Smartview (which is a pretty dumb name.) Often Miracast fails, regardless of its name.
I doubt MicroSoft will ever fix this, which is a petty for professional users, who could add a tablet and a pen for some quick notes and drawings. See here.
Casting TO the PC was never quite reliable, and it's even worse in Windows 11. The following work around seems to do the trick (or at least it does for me, 90% of the time).
The trick: when Connect is started as a window, and you enlarge it afterwards, it (temporary) allows you access to the titlebar. Just move your mouse to the top and the title bar appears.
1. Start up the Connect app (it opens in a window)
2. Make it full-screen (using the arrow symbol in the title bar)
3. Start casting from your (Android) Tablet.
4. You'll see an 'about to project' on your PC.
5. Wait a second or two.
6. Move the PC's mouse to the title bar and return to a windowed view by clicking on the arrows.
Notes on how to install the app on Windows 11 see here.