SSL In Postman trying to access Authorization

Following the API Startup Guide, we are seeing an error in the first steps. When we try to run the authentication for the sandbox we are seeing:

We are using:
auth.sandbox.roserocket.io - get 405 error
auth.network.sandbox.roserocket.io -644 SSL error. (tried this as thats the domain the sandbox is in)
our login credentials to network.sandbox.roserocket.io
The key as the client ID
and the secret

This looks like an SSL error at this point. Also, does this authentication need to be done every time? or once we have the token, it will not expire for that single app?