Do you have all the required documents from the manufacturer? Also a legal fapiao? The bike should be issued with a SH issued fapiao from the get go. However, that being said, if the bike has a larger than normal electric motor output ~400w give or take, it might be that there are restrictions on anything with a larger electric motor output than that. This is quite common in most parts of China, however with the rapid early adoption of electric vehicles this situation is changing rapidly, so who knows.
You'll likely need a good dose of perseverance and make connections with local Ch!nese electric riders in a club or such like to get abreast of the current legalities.
Just because you can buy and own it, doesn't mean it's legal...
With all things... TIC