Oh, I see. You are missing something in the progress for sure. For the attic thing to work I know you need the 'Secret Girlfriend' perk, not sure how many other things are necessary.
Yeah, you need to make more Progress with Meredith. The attic stuff is "extra." You need to go through a few things that will make MC more "enthusiastic" about spending time with Mom.
I looked at the code and the "Boys Will Be Boys" perk is required. You get that after the second Kissing scene. Use MC's bed (to lie down) and select "Jerk Off" and select "Meredith"
it was automatically copied from the last version of the game my dud, or you could find the save directory at C:/users/(urname)/appdata(checklist the hidden files)/LocalLow/Something Something Studio/Five of a kind