Ropsten has lower gas limit - around 4.7M and you can't set it yourself, since it's a public testnet. Gas limit value that you put in your settings can't override the blockchain's gas limit. You can try Rinkeby - it has 7693375, check the number at the top of the stats page: https://www.rinkeby.io/#stats
Check this related question: Is there a reason Ropsten doesn't have the same block gas limit as mainnet?