What happens when my store reaches a plan limit?

Your store keeps running. Only the action that would go over the cap is blocked, and the message tells you what your plan allows.

• Warning bar: from 75% of a product or order cap, a bar under the header reads Nearing your plan limit, then Plan limit reached, with an Upgrade plan link.
• Products: the cap counts published products only. Drafts are unlimited. At the cap, save the new product as a draft, unpublish another, or upgrade. If you downgrade while over the cap, shoppers see your oldest products up to the limit.
• Orders: on plans that cap orders, checkout stops at the cap. Shoppers are asked to contact the store owner.
• Staff, pages, blog posts, tax rates, shipping zones: adding one more past the cap shows "Your plan allows N…". For staff, pending invites count too.

Upgrade under Account → Subscription to raise the caps.