How can I fix unresponsive trackpad and keyboard on my MacBook Pro?

MistressAmanita wrote:

Trackpad and keyboard frozen. Externally connected peripherals work.

Any thoughts on fixes?

—A SafeBoot Start up your Mac in safe mode - Apple Support will sort many anomalies

Login and test. Reboot as normal and test. Caches get rebuilt automatically.

Unexpected keyboard and trackpad behavior can indicate a swelling, failing battery. These are symptoms of a potentially fatal (to the computer) battery issue:

•Unexpected trackpad and/or keyboard behavior.

•The gap between the display and the deck is not even when the display is closed.

•The gap between the bottom plate and chassis is uneven in places.

•Some of the screws that hold the bottom plate have popped out.

•The trackpad surface is higher than the surrounding deck surface.

•The computer "rocks" a bit on a known flat surface, such as a granite or solid-surface countertop.

Damage from swelling can progress at an astounding rate—even daily—so if you suspect the battery, get the computer evaluated as soon as possible.

The battery is not a user-serviceable item.

It always helps to know the exact model of the laptop. You can get this information by clicking the Apple menu and selecting "About This Mac".

If it happens to be a 2015 model, then it may be a bad Trackpad IPD Flex Cable which is a very common failure to that very specific model year (for both the 13" & 15" model....the last before the USB-C models).