Individual seller accounts are free to operate but limited in features. To grow your seller account you will need to upgrade to a Professional account, which costs £25/$39/month.
Go to Settings > Account Settings
Under the "Your Services" box, select "Manage"
On the next screen, you will have an option to "Upgrade" or "Downgrade" the Sell on Amazon Service.
If it says "Professional", no action is needed. If it says "Individual" then click upgrade
For more tutorials and how-tos, check out our Sitruna Guides series!