Canon 600EX-RT won't turn on at all

[jimlopes]

I own two 600EX-RT speedlite's.  One of them hasn't been used much and is totally dead.  I tried half a dozen different batteries and won't turn on.  

My 2nd speedlite turns on, but sometimes it doesn't.  The led screen sometimes is looks like it half on.  So this flash is proving to be unreliable on a shoot.

Canon has stopped supporting this version so I can't even get these repaired.  Is there a reset button on the device or anything else I can try to revive them?  Thanks

[jimlopes]

So I was about to put this flash to bed after trying everthing suggested here and not being able to send in for repair.  I decided to just hit the flash a couple of times of the side of my hand.  Figuring the old school way of trying to getting something to work.  Well, it actually worked and the flash fired right back up!  I couldn't believe it... could there been a connection inside that was loose?  What could explain just hitting it a couple of times for it to work again?

[normadel]

Sure, could be a connection somewhere. Battery terminal connections that you can't see, for example. Don't know how you can tell without opening up the flash, though, which I'd be very cautious about doing.