I was trying to create additional simulators in Xcode today and it kept failing with a weird error.

From Xcode:

And even from the terminal:

After searching for a while, there where some options suggesting I should reinstall Xcode from scratch but I really didn’t want to wait until Xcode finished installing again (it always takes a while). So I came across this post in the Apple Developer Forums that suggested killing the CoreSimulatorService and everything should work again. Some people there said that worked for them, so I tried it and it worked!

This is the command you should run to fix this error:

sudo killall -9 com.apple.CoreSimulator.CoreSimulatorService

I never had this issue before but fortunately the solution was simple.