Customer kms key is not working in china

Dear Sir/Madam,
I would like to use customer managed key in rds, but it does not work when i assigned the CMK to rds. it always takes the AMK(Amazon Managed Key) for some reason.

Versions:
Terraform version: 1.1.4
Terraform providers version: 4.27

I have also tried to used latest terraform provider version 4.50, but i had no luck.
Could you please help here?

BR,
Elumalai