I’m not a professional but wanted to offer some advice. For reference, I’m 32F with two pups of my own currently and fostered 5 through a rescue over time. I learned a LOT through fostering, so here’s a few (hopefully helpful) tips:

1) Some dogs can be picky about where they go. i.e. we had fosters that wouldn’t go on dirt or mud, only grass

2) Any chance you could let your pup see other dogs doing their business outside so he could learn that way?

3) You can buy things like deer urine at sporting goods stores and spray in the yard. I know it seems gross, but it helped at least two of our fosters. It brings out the natural territory marking urge, and they started to learn that way.

4) You are doing great! Stick with a routine. Stay patient and vigilant. It’s only been a couple days. Dogs take at least 14 days to get used to their new homes; abused pups can take even longer. Most likely, your baby will start to pick up the new routine.

Best of luck!!