How many parts you had before purchasing the part?
Theodore Wood said:
question is do we need to buy the parts from store or are they going to continue with shadow ops?
You can have up to 6 parts total. If you currently have 5 parts you will be able to only buy 1 part. If you have less than the 5 parts, you will be able to purchase the additional parts till you have 6 parts in total. After you have 6 parts total the purchase option will disappear from the store. This is intended and not a bug.