Why does the Shipping Zones page show "Upgrade to add more" instead of Add Zone?

Your plan limits how many shipping zones you can create. When you reach it, the + Add Zone button on Plugins → Shipping Zone changes to Upgrade to add more. Hover over it to see how many zones your plan allows. Click it to open your subscription page and upgrade.

To stay within your plan, combine areas into one zone. A single zone can hold many regions: click Edit on an existing zone and use + Add region to add more countries, states, cities or pincodes. All regions in a zone share the same shipping methods.