This is a known issue in V4S Kiosk application.
If a V4S Kiosk User has logged in to the V4S Kiosk application on a device and logs out. Another V4S Kiosk User then tries to log in to the V4S Kiosk app on the same device with a different V4S Kiosk User ID. Then the app does not allow to log in the second V4S Kiosk User, and the login screen keeps getting back to the login screen again after entering App Key, Email ID, and Password.
This is because the cache is not cleared for the V4S Kiosk application at the time of logout. As the Cache is not cleared on the phone the second V4S Kiosk User who tries to login the app is not able to log in. We will fix this issue and will be releasing the upgraded version of V4S Kiosk application.
As a workaround, if multiple V4S Kiosk Users are using the same device to log in to the V4S Kiosk application. Please clear the Cache of the V4S Kiosk application on the phone from the Phone settings button and then try to login to the V4S Kiosk application.
More information here about clearing cache for V4S Kiosk application