I'm in the exact same position!

Bought the Pro 7 Plus days after its release in China since I was currently working there and now I'm wanting to install the international firmware.

I've attempted several times and nothing seems to happen.
I rooted my phone by going to the fingerprint and security but it hasn't done anything except open up root options for individual applications, not the entire mobile.

Hopefully someone replies with a full explanation as to what can be done about this.