MacBook Pro late 2011 Trackpad not working after upgrade

Hello Med_,

Thank you for using Apple Support Communities. It's my understanding that after upgrading to Sierra, your MacBook trackpad has become erratic. I know my trackpad is a huge part of my everyday use, I can definitely understand your concern. I am here to help get this resolved with you.
You've done a great job so far! Next, I recommend resetting the System Management Controller (SMC). Resetting this system can resolve some unexpected behaviors. Follow the steps below:

1. Shut down the Mac.
2. Disconnect the MagSafe power adapter from the Mac.
3. Remove the battery. (Learn about removing the battery in MacBook and MacBook Pro computers.)
4. Press and hold the power button for 5 seconds.
5. Reconnect the battery and MagSafe power adapter.
6. Press the power button to turn on the Mac.

The LED on MagSafe power adapters might change states or temporarily turn off when you reset the SMC.

Reset the System Management Controller (SMC) on your Mac

If the issue persists, test this issue in safe mode. This will allow you to rule out third party software as the cause. Use the steps and link below to assist with starting in safe mode and additional steps:

1. Start or restart your Mac.
2. Immediately after you hear the startup sound, press and hold the Shift key.
3. Release the Shift key when you see the Apple logo appear on the screen.

After the Apple logo appears, it might take longer than usual to reach the login screen or your desktop. This is because your Mac performs a directory check of your startup disk as part of safe mode.

To leave safe mode, restart your computer without pressing any keys during startup.

Try safe mode if your Mac doesn't finish starting up

Cheers!

I was going to say, that sometimes a battery that is starting to swell up can put pressure on the underside of the trackpad and mess things up.

If removing your battery somehow reduced the pressure, and they you put it back in, you should keep an eye on that battery, as once they start to swell, it can get dangerous.

If it was the resetting of the SMC controller was what did the trick, then do not worry about the battery (unless you noticed it was swelling).

Note: the instructions for resetting the SMC on the Late 2011 Macbook Pro are:

If the battery is nonremovable

1. Shut down the Mac.
2. Plug in the MagSafe or USB-C power adapter to a power source and to your Mac.
3. Using the built-in keyboard, press Shift-Control-Option on the left side of the keyboard, then press the power button at the same time.
4. Release all keys, then press the power button again to turn on your Mac

<Reset the System Management Controller (SMC) on your Mac - Apple Support> In the middle of this web page

Late 2011 Macbook Pro

<https://en.wikipedia.org/wiki/MacOS_Sierra>

Apple menu icon -> About this Mac

Sorry but how u upgrade to mac sierra?

I Have same macbook and I can't upgrade it.