If you want to download photos from iCloud, you need to do the setting in Qubii App, please check how to set up in below.
Go Setting >>Backup item > Backup Camera Roll >> Turn on"Backup iCloud Contents”
Go Setting>>Click backup items >> Turn on“Download using Wi-Fi only"
Because download photos from iCloud will use a lot of internet data, this is why you need to use Wi-Fi to download photos.
You should be able to download your photos from iCloud to Qubii successfully while your phone connected to Wi-Fi.
*Please note that you need to turn off your 4G internet and switch to Wi-Fi on your iPhone setting. Qubii won't download any photos from iCloud except Wi-Fi connection.”
*Please make sure you have enough space on your iPhone. Downloading the photos from iCloud to Qubii, it needs to offload the photos from iCloud to your iPhone, then backup to Qubii.
*If you already did the steps above but the warning message still asked you to login something, you need to go your iPhone setting > click your name on the top > screw down to the bottom > click sign out >Then sign in again with your Apple ID. Then, Qubii should able to download your photos from iCloud.
It may take few hours to few days to offload your photos from iCloud to Qubii, it all depends on the quantity of photos and the Wi-Fi speed.