In your original MultiBit wallet, go to Tools > Repair Wallet (or something like that) and see if that works.
Not even trying that.
Here is a example pay attention:
I just created a new wallet using Multibit HD, then I created one and ONLY one bitcoin address which is:
1EzCCawrCJf33TzwAhEY4ffUBABSACk5cz
Multibit HD 12 words seen:
minor betray indicate trouble busy tragic easy diesel gravity window peasant satisfy
Now, if you go to the site and try yourself. It will provide you a lots of BTC address but how is that possible? If there is only ONE btc address linked to that wallet.
The site is not accurate. My coins still locked in Multibit and repairing or switching computers wont work. I also sent a message to the developers but I dunno they will care.
Multibit HD can use your 12 wallet words to generate an unlimited number of addresses.
I tested recovering your address 1EzCCawrCJf33TzwAhEY4ffUBABSACk5cz using the wallet words in that webpage. It was at the top of the list the webpage generated. If you had used multibit to generate more than one address it should have generated the same ones listed below that I copied from that webpage.
Using m/0'/0 the page generated these addresses.
1EzCCawrCJf33TzwAhEY4ffUBABSACk5cz
1Ma2L9vswGsHHwS3vLTvK1JqKkjdnJC8vy
1LiAzwrtrF37RrnE3LD9Z5KNvTo9mnHJ4V
1EsFnXZAkTwVKw2igqaQ13mgM8y5NQdp3x
18w26GebKe6TgNTLm5NzhgKowbdqYurQYj
Using m/0'/1 the page generated these addresses.
1G5THFo12YmrZWTLVHxmPnVWbodKn2jwKa
1PkkLzJYYf1KiLxk3MPxNEcgrr7mou6dVC
18Ejc8ynMDqs3pVnrEwz2QZVjSCURPprro
1AJadtfg6QKLVsRJiqNfBqu1jMupiS2ytY
12jXUrCirc1oQeTVXfvoH4z38bKJUEv3mj