For some reason, the package itself isn't available any more. Tried this via yarn and npm.
Log:
$ yarn add react-native-tooltips
yarn add v1.22.4
[1/4] 🔍 Resolving packages...
error Couldn't find package "react-native-tooltips" on the "npm" registry.
info Visit https://yarnpkg.com/en/docs/cli/add for documentation about this command.