Are you by any chance using an adblocker? If so, this might cause issues in the developer dashboard. Please try disabling any ad or cookie blockers in case you don't see the users and access button as seen on the image I posted above.
I created this new test application, disabled ad blocker and the button still didn't appear, I also tested it on different browsers. Then I tried to access the dashboard through my phone and the options appeared!
I'm not sure I follow the issue here - if your app is new it will be in Development Mode. When in development mode you can click the "USERS AND ACCESS" button in the top right corner to add users. Note that you'll need to add the email address that is attached to their Spotify account.
I am not using an ad blocker. I was able to log on in Safari and saw the "USERS AND ACCESS" button, but on Chrome the issue persists. I can now add users which fixes my problem, but there are probably other users who are still seeing the old version of the page.