Your Pro subscription gives you access to 5 devices at a time. If you try to download songs on more than 5 devices, you’ll see a message that says “Device Limit Exceeded”. This means you need to deauthorize an old device to proceed.
In your Android app, head to Settings > Devices to see a list of devices authorized right now. Tap "Remove" and then "Deauthorize" to confirm.*
In your iOS app, head to Settings > Pro Options > Devices to see a list of devices authorized right now. Tap "Remove" and then "Deauthorize" to confirm.*
*Please note that deauthorizing will delete any downloaded songs on the selected device.