I want to select other cloud service such as Google Drive, iCloud Drive

You can access Google Drive directly from Piascore.

If you use Dropbox or iCloud in Piascore log out it once.

• Download > Dropbox (or other cloud service) > Tap "unlink button" on the top right
• Setting > Detail > Cloud > Logout

If you don't use Dropbox or iCloud in Piascore, please tap "Cloud" in
"Download".