Ben,
Since we use Py3.6 when testing scripts in-house, let's rewind and try some basics ...
a. On a clean system, i.e. no python installed, please go to
https://www.python.org/downloads/, choose the latest Python 3.6
64-bit installer, double click and go through the installation steps. This will setup the appropriate binaries, as well as the env variables. Resolve should now automatically pick up Python now.
b. Alternatively set a global environment variable PYTHONHOME (
edit: probably better I provide
formal references than offer OS specific responses) and restart Resolve.
Regards
Shrinivas