I have the same problem. I tried to compile plugin with endpoint URLs corrected in the source code but unfortunately it doesn't work either.
Ok, I got it working (unfortunately, only with AWS China): https://github.com/great-qwerty/ec2-plugin
The list of the regions depends on he AWS SDK plugin version, and also of the account configured, not by ec2-plugin
why is this closed, it's still not work and the default endpoint is different in China or in Gov,
there is multiple problem here,
https://docs.amazonaws.cn/en_us/general/latest/gr/rande.html#cnnorthwest_region