Go to https://sprintr.home.mendix.com/ and find Your Project in the list. Go to the deployment tab and there you will find the ''Show application logs'' and ''show debugger information'' buttons
[obsolete]Unfortunately, it's not possible to access the logs from Sprintr for a Sandbox application. My suggestion would be to add the Logging module from the AppStore. This module enables you to have your application write all console log messages to the application and store it in an entity so that you can access the information from within your application. See also https://appstore.home.mendix.com/link/app/159//Logging-Module Ps: by default you won't be able to immediately import the module to a Mendix 6 project as the module was created in Mendix 5. However, you should be able to load the module into a Mendix 5 project, after which you can upgrade it through your modeler to Mendix 6. I still use this module in several Mendix 6 projects.[/obsolete]
Edit: wow how did I overlook those buttons
Here is a screen shot of the app platform for one of my sandbox apps. You'll see the three buttons I have circled that will enable you to access the logs for your sandbox app:
Hope that helps,
Additionally you could test the integration locally and monitor the errors in your 'Console' view. If you don't have a problem locally but you do in the sandbox, it might be that you are accessing a service inside of your network that hasn't been opened outside your firewall for the sandbox cloud server to access. It's a common issue for new folks to the platform.