App will not download

Purchased iPhone 11 Pro app is on phone with ☁️Down arrow Next to it. When I download message pops up states unable to install app no longer available in App Store. App was working fine on my iPhone XS even though it was removed from App Store in 2018. With app icon present on phone surely there must be away to download it from the cloud. Tried to contact developer which is what Apple suggested but have yet to receive a response. Any suggestions as to how I can install my app?