Tried with following api also:
API: https://users.app.lucidchart.com/documents/docs
Response:

Hi!

The only scope available for our OAuth 2 api is "data.service."  In this way you can not use an OAuth 2 token to access the document API's only to upload and refresh data to your account.

For the document API's you will need to use OAuth 1.0 as outlined below: 

https://www.lucidchart.com/pages/api_authorization

Can you give that a shot?

We have now published our available O Auth 2.0 scopes which includes a number of document related scopes.  You can view our new API documentation at the link below. 

https://developer.lucid.co/rest-api/v1/#access-scopes

Hi! Updating this thread with exciting news - we've recently launched Lucid for Developers a community space dedicated to supporting and connecting our users working with the Lucid API and our most technical features.

In this section the developers actually building Lucid’s APIs will be available to answer your most technical questions just like this one. Furthermore here we plan to announce new endpoints tools and guides to help you have the best possible experience developing on Lucid’s APIs. You can browse existing posts connect with other users with similar questions and goals and ask questions of your own by creating a new post or leaving a comment. Thank you and we're excited to hear from you!