1. Choose System Preferences from the Apple menu, and then select Keyboard.
2. Select "Show Virtual Keyboard and Emoji and Symbol Viewer in Menu Bar".
3. Click the input method in the upper right corner of the menu bar, and select "Show Virtual Keyboard", and the keyboard display program showing the key layout will appear on the display immediately.
4. Press the Delete key to observe whether the corresponding key in the keyboard display program is highlighted. If highlighted, it means that the key can work normally.
Step 2 Confirm that the Mouse Button is not enabled.
1. From the Apple menu, choose System Preferences.
2. Click the Accessibility icon in the System Preferences window.
3. Click Mouse and Trackpad or select the Mouse tab.
4. Uncheck Enable Mouse Button.
Step 3 Reset the System Management Controller (SMC)
1. Turn off the Mac.
2. Unplug the power cord.
3. Wait 15 seconds.
4. Reconnect the power cord.
5. Wait for 5 seconds, and then press the power button to turn on the Mac.
Step 4: Reset the nonvolatile random access memory (NVRAM)
1. Turn off the Mac.
2. Find the following key on the keyboard: Command (? ), options, p and R.
3. Turn on the Mac and press and hold the Command-Option-P-R key immediately after hearing the startup sound.
4. Press and hold these keys until the computer restarts, and then you will hear the startup sound again.
5. Let go of these keys.