Where do you see that? In the device’s page in TTN Console? (If yes, then the secret keys are correct, and indeed at least one gateway has received the device’s data, and TTN has determined which application and device the incoming data belongs to.)
You mean the device’s Data page in TTN Console? Beware that you will only see the data that was received since you have that Data page open. To (partially) see recent older data as well you can add the Storage Integration to the application; see Why application data is shown as historical? - #2 by arjanvanb
Are you saying you’re using some Payload Format function in TTN Console? If not, then TTN should simply show the hexadecimal representation of the payload.