With all four Zendesk Suite License types—Team, Growth, Professional, and Enterprise—you can purchase Marketplace Themes. However, the Zendesk Suite Team plan restricts access to the development side of the Theme, prohibiting the purchase of a Developer license or the creation of a customized Helpcenter Theme. To bypass this limitation, an upgrade to at least the Zendesk Growth Plan is necessary. This restriction is noted when purchasing a Marketplace Theme.
With all 4 Zendesk Suite License types (Team, Growth, Professional and Enterprise) you can buy Marketplace Themes.
However, if you have the Zendesk Suite Team Suite, you are not allowed to access the development side of the Theme. This is a restriction set up by Zendesk. As such you can not buy a Developer license for a Theme on the Marketplace. Nor can we create a customised Helpcenter Theme.
You will need to upgrade at least to a Zendesk Growth Plan.
This is mentioned as well when you want to purchase a Marketplace Theme