When you say you have the PSD file "synced," what do you mean?
If it's in your Creative Cloud Files folder, that's not where it needs to be to move back-and-forth with it between Ps and Fresco. It needs to be in Cloud Documents. To get it there, you can import it into Fresco by tapping the Import and Open icon on the Home screen of Fresco.
Once you bring it into Fresco, and it syncs to Cloud Documents from there, you'll be able to open/edit it back-and-forth between Fresco and Ps.
I had a bit of trouble figuring out, based on the little you wrote, what's going on, so please let me know if I've misunderstood.