The SlapOS user you just created isn't allowed to instantiate any service until its contract is validated (for a commercial use of SlapOS, you wouldn't want anyone to be able to instantiate something before checking he will be able to pay).
In order to validate the contract, you must first logout from your user account and log back to SlapOS ERP5 master at https://[IPv4]/erp5/login_form with "zope" user (= super user). Then go to https://[IPv4]/erp5/cloud_contract_module and type "%" in the Title search bar and type Enter. You should see one contract for the user you just registered.
Click on the contract, then Action - Validate as seen on the screenshot. Your user is now authorized to instantiate services.
The setup of SlapOS Master is complete. You can now start to request services available on your network.