I came across this issue when attempting to implement a custom tender application. Trying to create the tender through the SDK resulted in an error "500 Access denied".
The app I had created in the Sandbox environment did not have the correct permissions, so it made sense. However, after updating the permissions on the dashboard and uninstalling/re-installing the application on my device (adb uninstall, and wait for the clover app updater to sync)... the new installation did not have the updated permissions applied. I found if I looked at the installed apps and inspected the permissions there was only the few I had selected when I originally created the app.
Finally, I got it to work properly by unsubscribing our sandbox merchant account from the application via the Clover Market web dashboard. Once I had done that and uninstalled the app from the device, I re-subscribed to the application. After the installation finished I checked the permissions and saw all the permissions now correctly applied to the application. And now, things are working as I expect, and I am able to create tender buttons that appear in the register app!
Hopefully this gives you something to go on and give advice to others who come in contact with similar problems.
