The same thing happened here for weeks, and it was driving me nuts. I finally decided to look into the matter and found the culprit. I'm unsure how this will help others, but here's what worked for me. (Running Photoshop Beta on Windows 11.) First, I systematically quit the apps running in the background, checking the Shift+Ctrl+I shortcut in Photoshop after each quit. To start, I went through all of the apps running in the System Tray, but these all seemed fine. Next, I went through each suspect item in the Task Manager, and when I quit an app called Motiv Mix, the Shift+Ctrl+I shortcut in Photoshop started working again. Motiv Mix is a recording app that's also used to change the settings in a line of Shure microphones. I couldn't find any way to change shortcuts in the app, but it doesn't need to be running to use a Shure microphone, so shutting it down did the trick. Anyway, the app that's hijacking the Select Inverse shortcut in Photoshop on your computer could be different from mine, but I wanted to mention how I fixed this issue on my computer. Hope this helps! PS, I almost forgot: I also had to deactivate Motiv Mix from my Startup Apps window, so you may need to do this, too.
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