Game progress not showing logging in to 2nd ps4

My son has a PS4 at his mum's place and at mine. He purchased a game on my machine which he started at his mum's, but when logging back into mine, the game appears, but the progress hasn't transferred (and he needs to start the game again).

How can I fix this? His mum's PS4 is set as his primary one. I've tried all options I can think of, but would have thought it should be possible to start where he left off wherever he logs in.

Solution 1:

Cloud saving (having progress avialable on multiple consoles) Is only avialable to PS+ users, since you stated that he bought the game after he no longer had a PS+ subscription he / you would have to buy a PS+ subscription for cloud saving to be enabled. I don't know if you have access to that progress after the subscription runs out again though.