6mo Lab refuses to go outside

My husband and I just got a labrador retriever puppy four days ago. and I’m not sure if I’m equipped to handle this.

My husband picked up this 6mo puppy from an Amish farm. From what he told me, it seemed like she was living in a barn/outside, and the dogs weren’t in the house.

Since bringing her home (we’re in an apartment on the second floor, no fenced in outdoor area but lots of grass and pathways), she’s had potty issues. I expected this, not only with a puppy, but after learning that she was a barn dog. I figured she was probably pooping and peeing wherever with no proper training at the farm.

We’ve done everything we thought we were supposed to do from what we’ve been reading online. We’ve been crate training her, taking her outside after she eats naps and plays, and interrupting her and taking her outside when she tries to pee or poop on the floor.

This morning in particular was especially frustrating. I’ve been trying to get her on an eating/potty schedule, She typically goes potty around 5AM, eats at 6AM, naps around 8 AM, eats at 12PM, potty at 2pm, potty at 5:30-6PM, snd eats between 5-6PM. I always try to get her to go potty again around 8-9PM but she usually won’t. For the past like two or three days she’s been really good about peeing as soon as she goes outside at 5AM. This morning she would not go. I knew she had to pee because it had been almost 12 hours since she had last peed. I brought her back inside and she immediately tried to squat and pee on the rug, so I took her back outside. Again, she would not go potty. It’s almost like she was refusing to go outside. This seems kind of strange to me since she grew up outside and in a barn for six months prior. I’ve been trying to use treats and positive reinforcement when she does go outside, but it just doesn’t seem to be working.

I know it’s only been a few days, but I am just so frustrated and lost. If anyone has any tips I would really appreciate it. Would a trainer help with this?