Please connect your Ledger device.
If your device is already connected, please verify that another app is not using it or try disconnect and reconnect it.
Your Ledger wallet can store keys for multiple accounts. Each account can have multiple sets of four pre-generated keys: Owner, Active, Posting and Memo key. The set of keys allows you to change keys for each of your account.
Make a transfer using the Ledger to sign the operation.