I can't select multiple layers (cmd or shift)

@Yuta_Eric Hmmm, I wanted to see if I had the same issue as well...but, it appears everything is working ok. Doesn't matter what tool is selected (I even selected the Move Tool, and turn-off auto select, I can easily select the layers using either Shift or Command keys. What version of Photoshop are you using? And can you roll-back for the time being?

One of my students had a similar issue, and they were on an older M series, and they had the Sticky Keys is turned on. It's an essentially an accessibility feature designed for users who have difficulty pressing multiple keys simultaneously. So, when this is on, if you can't hold Command Shift Option P for some reason, with the Sriky keys on, you can simultaneously hit the keys one at a time, Command, Shift, Option, P (4 keystrokes one after the other!)... so, check your System Preferences - Accesibility-Keyboard- and make sure Sticky Keys is off

One more thing, I am a righty, so, I use the left keyboard keys, Shift and Command keys... try the opposite keys on your keybaord. There are also Shift and Command keys on the right. Who knows, maybe all these years pushing those keys on the keyboard could be wear and tear! It wouldn't be too costly to fix.