They should have run the "apron" (wall to roof flashing) all the way under
the "W" valley, flashing.
I think I'm seeing bare, wood - between the fascia and the roof.
You can try and slide a piece of flashing, under the aluminum fascia -
over lapping the existing apron.
If you use any mastic/sealant -
Don't use "tar"/roof cement -
Use "Quad" or "Solar Seal".
They didn't use roof-edge.