Friend not receiving invite, can they invite me?

I bought It Takes Two on PS5 and my friend has downloaded the friend pass version. However whenever I try to invite her, one of two things happens - either pressing triangle does nothing at all and I can't invite anyone, or I invite her but she doesn't receive the invite.

I've tried it from the PS5 version, running the PS4 version on my PS5 and even tried it from my PS4 Pro - the same thing happens. She's playing on PS4.

I've made sure that the consoles have a wired connection, I've ensured the game is on internal storage (even deleted and reinstalled), I've lowered my privacy settings and tried to invite her on different days/times. Nothing seems to work! I'm definitely logged in on PSN and it connects to my EA account just fine. She has also set up an EA account for it. We have no trouble playing other games online together. 

The odd thing is, she can invite me and we can start the game that way. But we're not sure if doing it that way around will only let us access the first chapter so we've been loathe to try in case that's as far as we can go.

So ultimately I guess my question is, if my friend invites me (who owns the full game) from her friend pass, can we play the whole game together that way?

Really disappointed that this doesn't seem to work straight out of the box (well, the digital box!), we've been excited to play it after seeing everyone raving about it! We just want the thing to actually work 🤦‍♀️