PlayStation says I already have Playstation Plus but Overwatch says i don't

Solution 1:

It's part of PlayStation's wacky permissions things:

1. Because you are a sub-account to your mom, you have limitations to what you can purchase. PlayStation Plus is apparently one of those limitations. It might also be more than your mom let's the account spend per month. It might be that it's more money than your mom has on her account. There are a bunch of reason why a sub can't buy.

2. Even though you are still covered by your mom's PlayStation Plus account as a sub, she can only have one "primary" PS4 console. So while you're playing on her console, everything should work fine, but on your new console, she does not (or at least I'm assuming she does not) have an account on it. She would need to log in you your console and declare it her primary PS4. But that means the original would no longer allow her to access PS+ content.

You're only real option is to go through the process of detaching yourself from her account and paying for PS+ yourself.