Unfortunately, having both stores open simultaneously was causing a severe quantum imbalance of all energy and matter in the universe. This would have resulted in a cataclysmic implosion back to a state before the Big Bang! That was a risk they just couldn't take.
Not really. The answer to your question is here... construct.net/en/forum/scirra-website/asset-store-36/cant-old-asset-store-asset-159328
If you know the seller's name, you might try contacting them in a thread they posted in or outside this site. Otherwise, you're out of luck and should maybe look for another template.