They have finished milking customers into paying for Final Fantasy VII Remake PS5 and now those that redeemed it previously on PS4 PS Plus will now get a free upgrade.
To coincide with that "Episode Intermission, the DLC featuring Yuffie Kisaragi, will be 25% off for a limited time!"
More from Kotaku:
https://www.kotaku.com.au/2021/12/final-fantasy-vii-remake-f…
Here’s how to install that upgrade.
If you don’t currently have Final Fantasy VII Remake installed:
Head to the Final Fantasy VII Remake store page on your PS5.
Under Add-ons, look for “FINAL FANTASY VII REMAKE upgrade for PS4 version owners”
Download it, and let it install. You’re good to go.
If you DO currently have Final Fantasy VII Remake installed:
Highlight the Final Fantasy VII Remake tile on your main menu and press the Options button on your controller
Then select Manage Game Content
If you can’t see a PS5 version of the game, head to the Play Game button and select the three dots
Finally, select View Product. You should see the upgrade there.
Using the same three-dots menu described above, you can now switch between the PS4 and PS5 versions at any time.
As Hybroid said it has to be done on PS5, per the instructions in the deal.
Also switch the "game" option to the left of "add to library" as shown in the screenshot if it still says unavailable.