you are supposed to enter you PIN at the latest four months after it is sent by Google or Google will stop serving ads to your site. So your account and site seem to be ok, but the PIN is missing. It seems to me Google has sent it to your address but you never got it, just ask google to resend the pin, don't create new account
Google says " How long do I have to enter a PIN? You'll have 6 months from the initial issue date to enter your PIN. If you have not entered a PIN within 4 months, we will replace the paid advertisements on your site with unpaid Public Service Ads. If you still have not entered your PIN within 6 months, your account will be disabled and your unpaid earnings will be refunded to the appropriate advertisers. "
I don't think you can open another account, but you should contact them for sure.. They will answer in 2 days max.
Why did u wait for 6 months... U must have requested for a new pin within 1 or 2 months after which the pin was believed to be sent... Just request them for new pin but i must say it is completely ur fault that u waited too long