You've recently funded your Steam Wallet using a new PayPal account or an unverified payment method that has had a recent increase in use. You'll be unable to use the Market for a few days while the funds are verified. More info...
You are logging into The Market from a device that has not been protected by Steam Guard for 7 days. More info...
You have recently reset or enabled Steam Guard, you must wait 15 days after Steam Guard was enabled. More info...
Your account must be protected by Steam Guard for at least 15 days. To remove this restriction...
If nothing further occurs to restrict your access, you'll be able to use The Community Market on 2/26/2015 1:16:43 AM.