Only Dutch organizations are required to register with a valid registration number. The platform is linked to the Dutch Chamber of Commerce website which automatically generates the organization data.
As a foreign organization it is possible that you do not have a registration number.
To register successfully, enter a fictitious number, letters or a combination of these in the 'Registration Number' field. Example: 123HG4
Click on then Search and Verify, you will see that you can enter other details of your organization.
You can succesfully register your organization.