Cloudbet is a hugely popular online betting platform with a variety of casino games and sports betting. However, due to betting laws in different countries, it's currently banned in the US, the UK, Italy, Hong Kong, and Northern Ireland.
On Android device, navigate to 'Apps' > 'Settings' > 'Security', enable 'Unknown Sources', then tap 'OK' to agree to enable this setting. This will allow the installation of third party apps and standalone APKs.