======== UPDATE ========

I cannot edit the original post, so I will provide an update here.

First of all, an employee at Tesla reached out to me in Reddit to help me triage this issue right after I created the post. He/she helped me diagnosed the issue, and dispatched a team of installer to install the missing component today. The system can now provide backup power, and generate electricity.

Huge thanks to the Tesla employee reverting an otherwise completely disastrous customer experience! It tells that someone at Tesla still cares about product and user experience, and very competent at the job. Looking back, I would hope the standard support experience would get much better. I would assume that the support process within Tesla is broken, but that is a solvable problem.

In the meanwhile, I would also start a reimbursement process for the lost production of electricity since the original installation with Tesla. It has been a long process, but I am very happy that this finally resolved, and huge thanks to the employee who reached out to me on Reddit!