I've tried this but the game would not see the save file for me.
Maybe due to the launch game save file (PS4) was a physical disc version, not sure. It's on the same region but no luck yet it being usable with this new Complete Edition (on PS5).
My base game was also a physical disc version (the same region as my actual PS4 which I bought as a bundle). Not really sure what could be going wrong in your case.