While the app is free to use and anyone can freely receive invites, one caveat is that you can only send invites if you have a paid iCloud+ account. This is a bummer, but it makes

Add another one to Apple's list of third-party apps that it has endangered, as Apple Invites threatens the livelihood of event planning app Partiful.

Alternatively, it’s a good way to annoy your Android friends by giving them work to do.