OnSong allows you to import content using a variety of content providers and storage services such as Dropbox. When you sign in to these services, the screen that appears is provided by the storage service and OnSong has no control over the authentication or authorization process. This allows your information to remain secure by sending your credentials directly to the third-party service. Once the authorization process is complete, the storage service returns a unique token to OnSong that is used for communication with the service.
Recently Dropbox appears to have changed this login screen in a manner that makes it incompatible with iOS 9. Since this is the only version compatible with iPad 2 devices, you are no longer able to sign in to Dropbox on older iPads. This results in the login screen placeholder text never hiding as you type and the "Sign In" button never enables. Pressing the "Go" button on the on-screen keyboard does not appear to send credentials to Dropbox to be authenticated.
If you are signed into Dropbox at the moment, don't sign out and you can continue to use Dropbox. Unfortunately, there is no way to sign in again since Dropbox has dropped support for iOS 10 and earlier and now requires iOS 11 and higher. Please note that OnSong will be dropping support for iOS 9 and 10 devices in 2020 and we recommend that you look for an upgrade path for older devices for best support and performance. It appears that iOS 10 and higher devices can continue to sign in to Dropbox through the OnSong app. Recommend that users on iOS 9 and 10 upgrade to a newer device for continued support.
There is a workaround for older devices to access Dropbox in OnSong 2020.3.
OnSong 2020.7 and greater requires iOS/iPadOS 13 or higher. We recommend updating your device to continue to receive updates and support from Apple and OnSong into the future.