When you go to the market always check that you have 5 slots available in your storage.
I'm sure that all Simcity BuildIt gamers have had this happen to them at some time, when they go to buy something in the Market, they have not had enough space to buy it. And, many times, they are really interesting products. But, if you make a habit of looking at the storage capacity just before going to the Global Trade, you won't get the unpleasant surprise of not being able to buy what you are looking forward to.