Struggling to potty train my 7 m/o Cockapoo

Hi all, basically what the title says, but let me give you some backstory first.

So Boo is a 7 month old Cockapoo and we adopted her from my mother’s friend 3 weeks ago today.

Now, the previous owner works a 9-5 job, so Boo was on her own in either a playpen or a crate for 10 or more hours a day (by the time she travelled to and from work) and only had 3 hours with the previous owner in the evening before she was being put back in the crate for bedtime. Rinse and repeat for 5 days a week.

The issue is, the prev owner would lay puppy pads everywhere – in the pen + crate and around the house to go on, but said she was toilet trained and only has odd accidents here and there. Well, either she lied or it’s something else, but Boo will not potty outside. I can stand out the garden with her for 15 minutes and she won’t go, but as soon as I bring her back in, she will go on the runner by the back door. It’s insanely frustrating.

I feel like I knew how to toilet train a dog, but now I’m second guessing myself. I had no issues training my cocker spaniel the 2 times I had to do it (yes, I used a giant re-washable pad at first, but that’s because I’ve had foxes in my garden and parvo is a big risk in my area) and he caught on incredibly fast. He was easy peasy.

But Boo? Impossible.

I let her out first thing in the morning and she will go do her business no problem, but as the day goes on, it’s like she refuses to go potty outside and would rather do it inside. I will let her out for 10-15 minutes every half an hour and the majority of the time, she won’t go and she will come back in and will potty on any sort of soft surfaces, so carpet, rugs, runners, sofa and the bed. We’ve stopped her from going upstairs altogether for this reason, unless it’s to go to bed and she goes straight in her crate.

I do the usual, positive reinforcement + treat when she goes outside and no reaction when she goes inside, just a swift redirect to the garden where she will just look up at me like I’m stupid and won’t finish her business. She even watches the other 2 dogs go outside, but it’s not sinking in.

I am at a loss. Has the prev owner made this more difficult by letting her go in the house as she pleases? I also don’t think it’s a settling in problem either because she was completely settled after the first few days, now it’s like she’s always lived here and she owns the place lol.

Any sound advice is appreciated.