"Sharing saves" doesn't work. Ren'py, the engine the game is made in, checks if a save was made on the device before it loads it, and blocks saves from other devices, since saves could include malicious code.
There's an "Upload/Download Saves" feature in the game, but for that up- and download need to be coordinated (it only goes through the Ren'Py server and saves are only kept for one hour). Otherwise, from what I've heard/read people complain about, saves transfered "manually" have started getting blocked entirely since a certain Ren'Py update, not sure which.