Yes I meet the same problem this week for my GLC300 2020, the TPMS problems resulting product_compliance@mercedes-benz.ca rejects to provide compliance letter to me and their online link https://www.mercedes-benz.ca/en/compliance-letter is definitely a fake trap aiming to cheat their customers, you can never submitting your requesiting form online through their portal as the system is always shows error occurs in the final submitting step.
Even if you email their product_compliance@mercedes-benz.ca goup, they find thousands of way to refuse provide a compliance letter, they will kick you back and forth with same message until you are dessperated.
I just want to be informed how to successfully get a "non-compliance" letter from MB canada, or any detaied steps to sue them to get that letter, currently I have confronted with dealership, the service group, but nobody gets any positive feedback.