I've installed the oidc plugin with instructions from:
On client side I've added:
* Client ID
* Client secret
* Redirect URI: https://moodle.gluu.org/auth/oidc/ , where moodle.gluu.org is my VM's FQDN. This value was suggested inside the settings of the oidc plugin.
* `Resource` inside moodle oidc settings should be empty.
* `client_secret_post` is the authentication method for token endpoint.
With above things in place, the oidc login works for me in my fresh installation.
* `Grant types` are:
authorization_code, implicit , refresh_token
* `Scopes` are: openid, uma_protection, user_name and email.
* `Response types` are code, token, id_token.
Altough these all values for scope and response type may not be necessary.
Hope that helps.