My iphone 11pro max is not displaying the slide to power off. I cannot open any apps and the screen is stuck in the application switching screen and i cant access anything. When i hold the side button and the volume button

If you hold the volume up and side button together and do not see the Slide to Power Off, then force restart the iPhone. Quickly press and release the volume up, then volume down, the press and hold the side button until you see the Apple logo and release. The iPhone should reboot. Test.

Connect Your Phone to PC or Mac, from ITunes Reset “as new” your entire Phone, if you have a backup restore.

Secondly, make sure you are holding Volume “Up” button and Power button both together

Regards