You've reached the selling limit for the number of items you can list. Account privileges for sellers may be limited until they establish a good track record with us and their buyers. The number of items you can list is limited until you have fulfilled past sold items. This helps us make sure you can deliver the level of customer service you need to succeed on eBay.
As you establish a good track record with your buyers through fulfillment of current sales, your limits will continue to increase automatically.