Your shirt(s) may be showing as currently unavailable or missing some sizes for purchase because we have received an overwhelmingly positive response to Merch by Amazon, and as a result, we are experiencing unexpected demand. At this time, we are working aggressively to increase our production capacity, but in the meantime we have limited stock and extended shipping times to ensure your customers receive their orders on time. We will stop limiting orders as quickly as possible. You can see updates on this in the Merch portal messages section. Thank you for your continued interest in Merch by Amazon.