The Dapper Go button appears when Dapper "sees" all of the storage drives of your DAP and when it has full access to those drives. (MacOS has security which will block apps like Dapper reading data you did not explicitly give it access to, including new SDCards etc)
If you have changed cards, renamed cards or done an upgrade of MacOS or otherwise changed your settings its possible that Dapper does not have a good reference to the DAP storage.
To fix this potential issue:
- Unlock the Dapper settings.
- Click the left hand storage area icon on the left of the main Dapper slider and re-select your first DAP drive.
- Click the right hand storage area icon on the left of the main Dapper slider and re-select your second DAP drive.
- Lock the configuration and, if necessary, restart Dapper.