OwnCloud 10.7 unable to authenticate

Problem/Motivation

I've been trying to set up a Drupal instance as an OpenID connect provider for OwnCloud 10.7. OwnCloud will send users to my Drupal instance so they can authorize the login, but when they are sent back to OwnCloud, there is an "Error in OpenIdConnect:The grant type was not specified in the request" message, and the log in fails.

I asked for help on the OwnCloud forums as well. https://central.owncloud.org/t/how-to-configure-openid-connect-with-drup... So far it's been over a month with no replies.

I've been reading up on Oauth and OpenID, but I'm not sure if that message means something is wrong on the client side, or on the server side.

I have been focusing on the OwnCloud client side in my troubleshooting because I've successfully configured a separate Drupal instance to authenticate with my Oauth Server instance. But with the lack of response there, I'm hoping someone on the Drupal side might be willing to help.

Any tips would be very appreciated.

Thanks in advance!