please, try to check the following two requirements; the second point is not included inside our tutorial because it should be the default but it may apply to you:
1 - in Solution Explorer, expand the References node and click the assembly listed in the error. Ensure Copy Local in the Properties grid is set to ‘True’.
2 - In the properties of the project, Publish | Application Files Tab, ensure the Publish Status for the assembly listed in the error is set to ‘Include’
Please, let me know if this fixes your issue so we may update our tutorial accordingly.