Why does request to REST API return `need_login` when I have a valid access token

I can successfully request an access token with the following request

https://{{SUGAR_HOST}}/rest/v{{SUGAR_API_VERSION}}/oauth2/token

{
"grant_type": "password",
"client_id": "sugar",
"client_secret": "",
"username": "{{SUGAR_USER}}",
"password": "{{SUGAR_PWD}}",
"platform": "base"
}

Aside: the documentation says to use something other than base|moblie|portal but when I do this request fails with error:

{
"error": "invalid_parameter",
"error_message": "Invalid platform specified."
}

I then use the access token returned by the above request to call an endpoint (passing the token as a Bearer token)

https://{{SUGAR_HOST}}/rest/v{{SUGAR_API_VERSION}}/JOB_Jobs

This fails with the error:

{
"error": "need_login",
"error_message": "No valid authentication for user."
}

Why does the access token not allow me, err, access?

V 11_20