unable to boot the simulator

I'm new IOS developer , my problem was when I run my application I have this message "unable to boot the simulator"

T start developing with xcode 7.3.1 and I oved to 8 but the problem exist yet for 2 week.

please help!

did you solved? suddenly, the same problem started here. Cannot use the simulator and crash entire Xcode. Need to force quit.

Same problem for me from the morning, Can not use simulator 😠

I think i solved.
I was running under El Capitan.
So, i installed the new OS Sierra and seems the simulator is working well!

After install the Sierra OS i just had an issue about code sign but solved by following this: https://forums.developer.apple.com/thread/48905?sr=stream

unable to boot the simulator
 
 
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