403 Forbidden Error when scraping a site, user-agents already used and updated. Any ideas?

As the title above states I am getting a 403 error. The URLs generated are valid, I can print them and then open them in my browser just fine.

I've got a user agent, it's the exact same one that my browser sends when accessing the page I want to scrape pulled straight from chrome devtools. I've tried using sessions instead of a straight request, I've tried using urllib, and I've tried using a generic request.get.

Here's the code I'm using, that 403s. Same result with request.get etc.

headers = {'User-Agent' : 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.157 Safari/537.36'} session = requests.Session() req = session.get(URL, headers=headers)

So yeah, I assume I'm not creating the useragent write so it can tell I am scraping. But I'm not sure what I'm missing, or how to find that out.