Trackpad not working MacBook Pro I am having issue with my trackpad of MacBook Pro Retina early 2015, As it was working properly a day before, the Hardware Keyboard and other things working properly. 

I did tried Reseting SMC, PRAM, but no luck, I am on macOS Sierra 10.12.6.

Any suggestions?
I would start with the following:


Go to Apple > System Preferences
Select the Trackpad preferences pane
Check your various settings under each of the tabs


If nothing there resolves the issue, then try booting into Safe Mode to see whether booting into Safe Mode makes a difference, either during or afterwards.

NOTE: Before proceeding below I recommend disconnecting any external devices (e.g. keyboard, mouse, etc). This also includes Bluetooth devices as well as USB.

Boot into Safe Mode

Follow these steps to boot your Mac into Safe Mode:


Fully shut down your Mac
Restart your Mac
Immediately press the Shift key and keep it down 
Let go of the Shift key when you see the login window (NOTE: If you have FileVault enabled you may need to log in twice).
Take a note of what happens (i.e. does your trackpad work, etc)
Exit Safe Mode by restarting your Mac as normal
Again, take a note of what happens (i.e. does your trackpad work, etc)


Now, if after you've gone through the above steps you find that:


your trackpad works during Safe Mode but not when you're logged back in normally, let me know.
it isn't working during Safe Mode at all, then it's time to test your hardware with Apple Diagnostics (see below).


Run Apple Diagnostics

Follow the steps below to run Apple Diagnostics:


Fully shut down your Mac
Restart your Mac
Immediately press the D key and keep it down until you see the Diagnostics screen appear
Wait for Diagnostics to finish (this typically only takes a few minutes)
Once complete, one of two things will appear on the screen:


a No issues found message
a brief description of any errors found plus further instructions

If the diagnostics test does find errors, take a note of what they are


Note: If pressing and holding the D key at Step 3 doesn't work, start again at Step 1 and, at Step 3 press and hold both the OptionD keys instead. This will try and run diagnostics from the internet instead, so you will need to allow more time for it to complete. 

Regardless, take a note of what happens and let me know how you went.