Amazon Cloud Drive was deprecated and the ability to upload files to the service was removed by Amazon on February 1, 2023. As such, Mylio Photos no longer supports Amazon Cloud Drive as one of the options for a cloud device.

You can find out more about Amazon's decision to stop the service on their FAQ

If you have Amazon Drive as one of your devices in your Mylio account, make sure to add at least one other Vault to your account, synchronize all your devices, and then remove Amazon Drive.