How can I force restart my iPhone 15 Pro Max?

Try performing a hard reset: first click the volume up button, then click the volume down button, then click and hold the sleep/wake button. The "slide to power off" message will appear, but just keep holding the sleep/wake button. The screen will eventually turn off, but again, keep holding the sleep/wake button. Once you see the Apple logo, you can let go of the sleep/wake button.

Try double-tap the screen with 3 fingers.

You may need to vary the speed of the double-tap to nail it.

If no luck, you can perform a Forced Restart

Force restart iPhone - Apple SupportApple SupportOfficial Apple Support › guide › iphone › ios

Bob Timmons wrote:

Try double-tap the screen with 3 fingers.

You may need to vary the speed of the double-tap to nail it.

If no luck, you can perform a Forced Restart

Force restart iPhone - Apple SupportApple SupportOfficial Apple Support › guide › iphone › ios

To add more context, Bob is suggesting that you may have accidentally zoomed in on your iPhone screen (an accessibility feature that you may have accidentally turned on). If that's the case, tapping with three fingers may un-zoom the screen and fix your problem.

3 middle fingers

Works for me every time when I zoom the screen and want to back out.