Hello,
I moved your topic to Community Support, where people ask for help.
As pampiermole alluded, this can happen when you don’t have connectivity. When Sim Update 11 came out, and the servers were getting slammed, I lost connectivity to the Marketplace, as well. I didn’t have my online services disabled, but simply navigating off of the Marketplace and to another screen like the World Map and then back to the Marketplace brought it back up. That may or may not work for you, depending on your circumstances.