Microsoft Graph new tokens not working with reousrce api calls without invoking the graph explorer first

Question

Hello, I am requesting an access token based on shared secret. I will always be getting one successfully. However, if I use the bearer token with a workbook API I get 401. Only if I go to the graph explorer and request access token (without even using it and just using the tokens from the above), it will start working. The documentation is saying that the session is optional and API will work without it. So what happens when I click the "access token" icon that is required for my sessions to work? What should I add to the API calls? Thanks, Rony