MacBook Air 2017 not recognizing keyboard or trackpad after login

Sounds like a hardware issue of some sort which will need to be repaired. Since both the built-in Trackpad & Keyboard are having issues.....more than likely the Trackpad Flex Cable and/or the Trackpad itself is bad (most likely from accidental liquid damage since the connector is just below the gap at the top of the Trackpad). The fan running at high speed all the time is also another indicator since this happens if one of the sensors is not responding correctly. It is a very common occurrence on the MBAir 2013-2017 models that I support for my organization. FYI, the built-in Keyboard is connected to the Trackpad which is connected to the Logic Board through the Trackpad flex cable...so if one of the intermediary items fail, then the keyboard won't work either.

You can try running the Apple Diagnostics to see if any hardware issues are detected. At the very least I would think it will report a sensor issue with the keyboard and/or trackpad.

Ruskes wrote:

Reseting SMC is like working in the dark. Did it work on not ?

Use the verify method

Hold the SMC reset keys till you see the MagSafe plug change the color (very briefly) so watch it

Good point. I personally like to power on the laptop (usually an Option Boot where I let the laptop sit at the Apple boot picker menu so I don't risk corrupting anything when it powers off). Then I press the Caps Lock key so the Caps Lock LED is lit. Then perform the SMC Reset. The Caps Lock key should immediately go dark if the SMC Reset was successful.

To make sure a PRAM Reset is performed correctly I like to hold the PRAM Reset keys for at least three chimes (the USB-C Intel models will only allow two chimes at most....some only one).

Thanks for sharing as I did overlook that portion of the OP's post.

Reseting SMC is like working in the dark. Did it work on not ?

Use the verify method

Hold the SMC reset keys till you see the MagSafe plug change the color (very briefly) so watch it