macbook pro 2018 keyboard backlight

Please reset NVRAM / PRAM: Reset NVRAM or PRAM on your Mac - Apple Support.

You have already stated that reset SMC didn't help. But still try again with power adapter plugged-in.

reset the SMC of your Mac: How to reset the SMC of your Mac - Apple Support

Also be sure to use the left & right keys appropriately.

If None of the above didn't help then please contact Apple support / Service.

Please check if you have same issue in safe mode. (May take longer than your normal/usual boot)

https://support.apple.com/en-us/HT201262

Note: Safe mode prevents your Mac from loading certain software as it starts up, including login items, system extensions not required by macOS, and fonts not installed by macOS. It also does a basic check of your startup disk, similar to using First Aid in Disk Utility. And it deletes some system caches, including font caches and the kernel cache, which are automatically created again as needed.

Elghobashy wrote:

The keyboard backlights only lights up before logging in after logging in it doesn't work and the adjust keyboard brightness is not there .

I tried restarting my computer and reseting the SMC but nothing happened.

for backlight issue:

Try resetting NVRAM/PRAM http://support.apple.com/kb/ht1379

Please see Adjust the brightness of your backlit keyboard - Apple Support.

Hope you have already tried this.

Check in another new user / guest user if you still have same issue.