Unable to subscribe to Planet Scope AUM - Tier 2 1x

I tried every video subscription package and received an error message as follows:

This seems to have nothing to do with my location. When I choose Planet Scope AUM - Tier 2 1x, it still prompts me for the above error; No matter which order I place, it always reminds me so. Why?

Please see this post.
Customers from China has to contact Planet sales or partners channel, rather than using self-serve option.