It’s 2021 and ive had this issue for at least a year on my MacBook Pro 15inch 2015 model. the trackpad often keyboard as well, stops working. This can be when I’m in the middle of doing something or when I have left the Mac on standby whether this be with the lid closed or not. sometimes it fixes itself when I reset the SMC, sometimes when I just restart it and sometimes it literally takes about 15 resets including the SMC. it’s such a random issue with out anything clear about what’s causing it other than software updates. I’ve updated a few times now from high Sierra to Catalina and problem is still apparent. I never had the issue before the high Sierra update so I assume it’s this. if anybody has any ideas or heard anything from Apple or a repair shop please let me know!!!