You can't sync directly from one device to another, instead all syncing is handled by the cloud server, which is where all the master images are stored. So changes made on your android device would first sync to the cloud server, then when your iPad next connects to the cloud server it should receive those changes. In this situation where changes made on one device are not appearing on another device, it's first necessary to determine which link in the chain is not working correctly. To do that, you need to login to your Adobe account at lightroom.adobe.com which will give you a direct view of your assets on your cloud server. If the changes are not showing there then the broken link is obviously between the android device and the cloud server, but if they are showing there then the broken link is between the cloud server and the iPad. Determining that will help focus attention onto the specific area of failure.