[2021] Cross-Save and Cross-Play

Hi

Could someone explain to me how XSave and XPlay work with Ubisoft games? I'm looking at my PS4 screen and it says

"Cross-save functionality is available: your profile, including progression, all purchases and inventory, is automatically shared".

This to me suggests that if you have purchased something on PC you can use it on your PS4, including the main game. So why can't I load the game on my PS4?

I purchased the game for my PC when the game was in its infancy but soon switched to my PS4 when they had it for free in PS Now. I have just ceased using my PS Now account as I wasn't really getting any benefit from the membership given that For Honor was virtually the only game I actually played. Well, as I've now given up my PS Now membership I can no longer play the game on my PS4 despite buying virtually all the DLC and expansions, including the latest 3 heroes.

Am I doing something wrong? Should I be able to play on my PS4 as I have a full version for my PC; in fact I have 2 copies as one was free via Ubisoft's give aways and the other I purchased I believe on Steam.

Could someone correct me if I'm wrong please as I don't really want to have to pay £8.99 a month to play a game that's supposed to be Free to Play.

Thanks in advance.