to people who are having issues with this trophy unlocking, THIS is the solution that fixed it for me.
Step 1: Back up your saves (USB or PS Plus cloud storage)
Step 2: Delete your save games, not profile data (go to Play Campaign and delete each save)
Step 3: Start a new game "Advanced" and choose "First Assignment" level
Step 4: Finish the "First Assignment" level and proceed to get the "Mothers Day" mission
Step 5: Complete "Mothers Day" mission and enjoy your platinum
thanks goes to a guy called Fidget on youtube who gave me this method. please say thankyou to him on there if it works for you aswell :)